There is one important exception to the translator rule, and integral to why the FCC decided to allow AM stations to have FM translators. If the station is a daytimer, the FM station can continue to air programming even though the AM station is turned off for the day (doesn't apply to WMTM). The FM Translator also has to be inside the contour of the daytime AM signal, but is not limited by the AM nightime contour.
This question though opens up a lot of "cans of worms" that I've been seeing as I review radio stations.
If the AM station is not transmitting in stereo, can the FM station be in stereo?
Can an FM translator have HD2/HD3 channels unrelated to the AM station?
Is there anything wrong if the FM station is actually the source and is actually feeding the signal to the AM transmitter?
I'm also seeing a lot of these situations "rebranding" their station using the FM. If I have Wxxx-AM with translator W2xxZZ, and my station IDs itself as "Wxxx-FM" when no such station exists, am I over the line? (or is the legal ID at the top of the hour all that matters?)