Here's how I do it:

First, export your BiaB song to a MIDI file, then import that MIDI file into your DAW of choice.

I haven't done any RealDrums/RealTracks migration to my DAW, but I believe that you would export (render) these as individual WAV (or other common audio format) files, and then, like the MIDI tracks, import these audio tracks into your DAW.