I recently purchased an Atlas Trainman N Scale set including their N Scale Code 65 "True-Track". Are all N scale locomotives and rolling stock compatible with any N scale track or do I have to use code 65 track?
Short answer: almost everything will be compatible with almost any code track, except for some very old, unique, or non-American locos and rolling stock.
Code 80 (Atlas Snap Track, Bachmann EZ Track, Kato Unitrak) - Anything will run on it.
Code 70 (Micro Engineering) - Anything will run on it.
Code 65 (Atlas True Track) - Anything except maybe some obscure older equipment.
Code 55 (Peco or ME) - Anything except maybe some obsure older equipment.
Code 55 (Atlas) - Most Picky, will handle most modern production equipment except MicroTrains cars with "pizza cutter" large flange wheels. Even some current production Atlas equipment has problems on C55. Older equipment, pre-mid 90's will be questionable.