One way would be to use 'F5'

Go to bar 25 and press F5 to bring up the edit settings menu. In the top section, right hand side, press the 'realtracks' button. Select which BIAB track you want to place the soloist realtrack on, select the realtrack you want to use, and press ok. Then 8 bars later do the same thing except clear the realtrack (or go back to the previous realtrack if you had a rhythm realtrack there before).