So you just have the wma RT&RD's ? if you have the wav as well they will just work else you can convert the wma to m4a.
Just rename the bb\RealTracks\Library to LibaryM
and bb\RealTracks\Direct Input\Library to LibaryM
So you convert all the wma to m4a in:
bb\RealTracks - Demos
bb\RealTracks
bb\Drums
then copy all the XT2/ST2 from the BBWin to BBMac as well as the midi supertrax stx, and songs SGU, and styles STY etc..

http://www.pgmusic.com/forums/ubbthreads.php?ubb=showflat&Number=236483#Post236483

If you don't want to go through that you might be able to contact sales, tell them your story and you might be able to pay just for the hard drive and get the Mac Tracks on it ?