There are lots of things that come into play here in both the T295 route and the SAC-V195-SJC but the bottom line is, just like in VFR, the FAA expects you to be responsible for your own terrain avoidance, communication and navigation. MOCA, MEA, MIA, MVA, MRA, MSA, MCA, OROCA are all there to guide and assist you but ultimately you can request whatever altitude you want (ATC does not have to grant the request though and will deny an unsafe altitude) and it is your choice to accept or decline an altitude assignment from ATC.
Indeed in some cases, it may be preferable or even necessary to accept a lower altitude such as when executing a Contact Approach, Oxygen requirements for MEA not met or just overall convenience. OROCA's for example cover nearly 4000 sq. nm (1 degree x 1 degree + 4NM overlap on all sides) whereas a VFR MEF on a WAC is 10% smaller at 3600 sq nm (1 degree x 1 degree), on a Sectional it's ~900 sq nm (30' x 30') and on a TAC its ~225 sq nm (15' x 15').
For example, if you look at the Enroute L-4 the OROCA for the area 33N to 34N and 117W to 118W is 10,600 ft which indicates the highest obstacle in the area is 8,600 but if you switch to the WAC, the MEF for the same area is only 6,100. Going to the Sectional, the SW section of 33N to 33 30' N and 117 30' W to 118 W has an MEF of 2,100 and if you go to the TAC the SW section of 33N to 33 15'N and 117 45' W to 118W has no MEF listed as the MEF is sea level or 0 ft. The V27 route reflects this with a MOCA altitude of 2,000 ft but if I were cleared direct SXC from somewhere off route, I would, by OROCA standards, have to climb to 10,600 ft. Why?
The mountains 4NM NE of the quadrant at 34 04' N and 116 56' W add 4500 feet to the IFR altitude. There is a mountain 4 NM Northeast of 33-34N 117-118W section that is 8,600 feet. OCA standards state plus 2,000 ft for mountainous terrain putting the OROCA for the area at 10,600 which is 4,500 higher than the WAC, 8,500 higher than some areas on the Sectional and 10,600 higher than some areas on the TAC.
There are plenty of other examples where MEA's are higher than necessary due to Navigation. Remember a MOCA provides navigation assurances out to 22NM from the VOR Station and beyond 22NM it is only providing obstacle clearance. If VOR stations are sparse (more than 44NM apart) or if a particular VOR is known to be unusable at certain altitudes, you may have a higher MEA. Such is the case with V171 in Wisconsin, Indiana & Kentucky.
Coming into Louisville VORTAC (IIU) from the SE the MEA is 2600 and coming into Terre Haute VORTAC (TTH) from the NW the MEA is 2500, the surrounding terrain is non-mountainous (MEF + 1000) and only rises to a maximum of 3,200 ft in the broader area and there is no MCA at any of the checkpoints so why is there a 7,500 foot increase up to 10,000 foot MEA and a MOCA of 3,000? The VOR stations are too sparse and the route between them covers 114 NM. A MOCA altitude only guarantees NAV reception out to 22NM which is near the 90th percentile of range for a 25NM terminal VOR and a low altitude VOR only transmits out to about 40NM. While both IIU and TTH are High-Altitude VOR's, at low altitudes they are only reliable out to 40NM but TTH is in the facilities directory as having an unusable DME beyond 27NM below 3,500 (which coincides with SCOTO and the increase in MEA/MOCA from 4000/3000 to 10000/3000) and IIU is listed as being unusable below 10,000 on R285 through R339 so the solution for VOR coverage is to have an MEA of 4,000 for segment from TTH to SCOTO due to the DME. At SCOTO, allow an enroute climb to 10,000ft so you are in reception range of the high altitude transmitter of TTH by the time you pass 40NM and you are in reception range of IIU.
A bit further to the NW on V171 this time in Wisconsin between Nodine VORTAC (ODI) and the Farmington VORTAC (FGT) you have an MEA of 3000 leaving ODI increasing to 5,500 at EMILS but the MEA continues at 3000G for GPS NAV. Again all the surroundings and other data shows no immediate reason why there's an increase and if I were on GPS, I can stay at 3000G. Why? EMILS is 27 NM from station ODI, beyond the 22NM the MOCA provides and the DME at Farmington, which is required to find the first fix on course at ELIKE, is listed in the facilities directory as unusable below 4,000. If you have a GPS however, you can use the GPS information to provide the DME information at lower altitudes or you can even program in the ELIKE fix directly and not rely on DME at all.
These examples are an excellent example of why it is always a good idea to carry VFR charts and a facilities directory for the area you will fly through as it may provide important information as to why a particular route has a particular altitude.
The actual regulations are, as with most things in the FAR, a huge mess of conflicting information.
91.177 says you can go below an MEA but not a MOCA provided you have adequate navigation signals.
FAA Order 7110.65W governing ATC procedures and Effective December 10, 2015 has several exceptions, notably section 4-1-2 which allows reduced altitude and distance separation when being monitored on Radar, Section 4-4-1 which requires a route be above MIA not MEA and Section 4-5-6 which matches 91.177 and section 5-6-3 which allows vectors below other minimums
Further the FAA Instrument Procedures Handbook says many of the same things but has this to say about TEC routes and MVA's:
TEC Routes: ATC Provides radar monitoring and, if necessary, course guidance if the highest altitude assigned is below the MEA.
MVA: Because of the ability to isolate specific obstacles, some MVA's may be lower than MEAs or MOCA's or other minimum altitudes depicted on charts for a given location. While being radar vectored, IFR altitude assignments by ATC are normally at or above the MVA.
So lots of information all of which boils down to altitude is up to the PIC and the PIC is responsible for any issues that might arise from the selection of a non-published altitude.
Specifically regarding T295, the area is designated in 95.13 as mountainous thus OCA minimums are +2000 ft. Along the route from SASHA to SAGES, theEA is 6,100 and there is a 4,200 ft mountain just SW of SAGS intersection that is less 1/2 mile off the course. Thus the published MEA is related to obstacle avoidance and 6,400 is correct. As for flying at 6,000?
The area is white indicating a high probability of being in Radar contact, KAVP (just SW of LAAYK) is one of the first airports in the NorthEast TEC Routes and the MVA's for the area all seem to be in the 5,500 or below thought its difficult to really be certain given the lack of landmarks on FAA published MVA charts. So it seems the assigned altitude falls under the radar contact operations permitted below MEA.
The area for V195 between SUNOL and ECA is also designated mountainous terrain and there are several obstacles in the area that are close to 2,000 ft but MVA's for the area appear lower in some areas.
