You could also just render your biab tracks to wav files, saving them to an appropriate file when you do it. Close out of biab, open up reaper, import the files to tracks, and away you go. With rendering in biab [or RB], you don't technically need to drag and drop. It just adds a convenience factor, far as I can tell. But when you drag and drop, it still needs time to render those files anyway. So either or, same thing.

Dan

My YT Channel- http://www.youtube.com/user/dfizzbom