Wow!! I should have explained a bit more:
On the night I thought of this I had 2 copies of BIAB running at the same time, same song, slightly different chords but both all RTs, and I noticed the arrangement seemed incredibly busy when I pressed play on the top copy. I pressed stop and "the song carried on" as somehow the 2nd copy had also started playing, nearly in time but not quite. I could tell that from the drum track.
The "front" copy had needed to regenerate but I don't remember about the "back" copy.
I have tried to duplicate but with no success of course
I remember reading about the subject mentioned by Mario and this is why I started a new wish as somehow my computer showed that linking 2 BIABs could be done; it worked by accident so maybe it could work by design.
Alyn