I've used quite a number of free biab backing tracks for jazz standards with good results but I have to admit it's not exactly easy. Generally, I open in biab and convert to all realtracks with realtracks generated solos to provide raw material and to run through it playing to the chord sequence. Then I open it in realband and do a little mixing before saving as a file AND individual wave files.

That way I can open it in reaper to use as a very listenable set of backing tracks that I can play along to while hearing the realtime fx applied to my guitar input as I play. Finally, I can mix down choosing from the various solo parts (from the realtracks set or generated solos or my playing) to produce the final studio recording.

So the only thing I'm really using for free is the chord structure input. Everything else is added. But the results are satisfying.