Not sure if the MMAC ports used XA audio but it wouldn't surprise me....it's not a PS1 exclusive format (some Saturn and PC titles used this in the past) and is an eadequate compression format in place of cdda. Course even if they do they'll be packed in a console exclusive format so getting to them would be a chore.
protoman: I have the XA files sitting on my HDD at this very moment. As far as I can tell BGM.XA = Megaman 4/6 NES audio, BGM2.XA = Megaman 4/6 Arranged audio...Extra tracks used in the menus/credits (Bass's theme, Let the Wind Tell Him, etc) seem to be primarily found in BGM2.XA.
I'll register so that you can pm me the info for the ftp upload.
Also if you have interest in any other soundtracks let me know. I have an audiorip for the Misadventures of Tron Bonne (Soundtrack was never released to my knowledge), Megaman Zero 1-3, Megaman Battle Network 1-3. Tend to collect import game osts so may have some you'd be interested in for your MISC section as well (Castlevania: Symphony of the Night, Phantasy Star Online Episodes 1-3).