RealBand is basically PowerTracks that calls on bbw2.exe that is just Biab that runs silently in the background, it generates up tracks, renders them to RealBand's temp folder that are then loaded into RealBand tracks.

So basically this in what the BBPlugin does within your DAW,
so you have the Band in a box plugin you load in your DAW,
it then calls on bbw_64.app that runs silently in the back ground,
it generates the tracks, renders to aiff into the SavedTrack folder,
you then can drag them into the DAW.

The future of the BBPlugin should be to generate and play the RT RD direct from the source files.
This way the tracks will generate instantly, quicker than Biab, load frozen SGU's,
no aiff/wav files will be rendered until you are happy with the results
then as you drag them out of the BBPlugin into the DAW track they will be rendered.
With the Sends now in the BBPlugin you could leave them in the BBPlugin and just render the DAW session to wav without the BBPlugin ever have to render to file.

There is also a ReWireVST Mac/Win that will let you slave any slavable DAW to Biab.
https://www.pgmusic.com/forums/ubbthreads.php?ubb=showflat&Number=648011
You will need BB21Mac for the plugin to work.