I'm a newbie on Genos arranger, but I know very well BIAB.
Both Yamaha arrangers and BIAB use styles having the .STY extension.
But, there is a huge difference : keep in mind that Yamaha arrangers use several bars of a MIDI data for the A section for example. Let's say 8 bars for the A section.
In BIAB, you do not have any 8-bar A section. You have several - up to 200 or more cells - cells of 1-bar or 2-bar length. So, you will to assemble these cells to get a 8-bar section. But, in these cells, you will have a postfill bar, you will have dedicated cells for a given chord, many cells for bar#1, many cells for bar#2...or a for a given bass line...We call that 'masks'.
Furthermore, a BIAB styles has only two variations (A & B), two endings and you have no intros.
The approach of the two systems are really different. Just recall that BIAB is NOT a real-time arranger.
So, converting BIAB styles to Genos styles can be done, but it can't be done well.