Well, I'm still not sure how to sort this all out just yet, but I did find a quick solution. In BiaB, I can right-click the drum track at the top and select the "Save RealDrums as Wav File", then import that straight into Sonar to replace the previous RD track out of RB that only had the two variations. So, to summarize what I did for the current song I'm working on:

1. Entered the chords into BiaB and got the arrangement very close to complete with the right instrumentation.
2. Opened the same song in RB and exported audio tracks to a folder.
3. Imported all those audio tracks into Sonar.
4. Went back into BiaB and exported the RD track only (the one with 4 variations).
5. Imported that into Sonar to replace the first imported drum track.

It seems to be the long way around but it worked and hopefully I figure out styles and RD so I don't have to do this every time.
I would not have had to do steps 4 and 5 if the RD track came into RB the way it was in BiaB but I'm just trying to get something to work now and figure out the details for the next tune.

Do people post songs here?