I don't know how fast Parallels is these days but it might be a way to solve compatibility issues that seem to keep popping up.
The main Biab Win app should run fine, with the Win BBPlugin you might be able to set the generated SavedTracks folder and save it with SGU to a shared folder this might then load into the Mac BBPlugin if the Plugin it's self has no compatibility issues (not bbw4 app that gens up the tracks) ?
You could batch convert any Mac RT RD to wav as Mac will read wav but Win won't read aiff/m4a. You will need to convert the m4a demos to wma also.
The other issue was the Library in RealTracks & RealTracks/Direct Input folders Mac calls it LibraryM (as Library would not work) so you need to create a symbolic link for Library to LibraryM.

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