Negative. N numbers are but one way. From 47 CFR 87.107I thought using tail numbers was an FCC requirement.
(a)Aircraft station. Identify by one of the following means:
(1) Aircraft radio station call sign.
(2) The type of aircraft followed by the characters of the registration marking (“N” number) of the aircraft, omitting the prefix letter “N.” When communication is initiated by a ground station, an aircraft station may use the type of aircraft followed by the last three characters of the registration marking. Notwithstanding any other provision of this section, an aircraft being moved by maintenance personnel from one location in an airport to another location in that airport may be identified by a station identification consisting of the name of the company owning or operating the aircraft, followed by the word “Maintenance” and additional alphanumeric characters of the licensee's choosing.
(3) The FAA assigned radiotelephony designator of the aircraft operating organization followed by the flight identification number.
(4) An aircraft identification approved by the FAA for use by aircraft stations participating in an organized flying activity of short duration.
(b)Land and fixed stations. Identify by means of radio station call sign, its location, its assigned FAA identifier, the name of the city area or airport which it serves, or any additional identification required. An aeronautical enroute station which is part of a multistation network may also be identified by the location of its control point.
What makes this further irrelevant, is there is no requirement that a station actually identify itself on each transmission like there is in other services.(1) Aircraft radio station call sign.
(2) The type of aircraft followed by the characters of the registration marking (“N” number) of the aircraft, omitting the prefix letter “N.” When communication is initiated by a ground station, an aircraft station may use the type of aircraft followed by the last three characters of the registration marking. Notwithstanding any other provision of this section, an aircraft being moved by maintenance personnel from one location in an airport to another location in that airport may be identified by a station identification consisting of the name of the company owning or operating the aircraft, followed by the word “Maintenance” and additional alphanumeric characters of the licensee's choosing.
(3) The FAA assigned radiotelephony designator of the aircraft operating organization followed by the flight identification number.
(4) An aircraft identification approved by the FAA for use by aircraft stations participating in an organized flying activity of short duration.
(b)Land and fixed stations. Identify by means of radio station call sign, its location, its assigned FAA identifier, the name of the city area or airport which it serves, or any additional identification required. An aeronautical enroute station which is part of a multistation network may also be identified by the location of its control point.