It is possible to make a workaround on that using RealDrums. First generate a drum track, either RealDrums or MIDI drums, then copy that track to one of the lower tracks that aren't the BB assigned tracks. Then kill or mute the BB drum track and apply the push. That should leave the drums going and all other instrument tracks pushing. I would likely assign the push in BB before exporting to RB and I'd do the export of realdrums twice, once sans push for the keeper drum track and once with the push to get the other tracks.

To do the whole thing inside of BIAB:

Inside BIAB, I'd try recording the Drum track to the Audio track first, then assign the pushes and do a Save with Patches and Harmony and uncheck the auto-generated drum track such that the song loads without those auto drums but with the recorded drums on the Audio track. To record the drums to audio, first mute all the other tracks, then set your soundcard to WAV (or the line input if using hardware MIDI synth) and then arm the Audio track to Record the drum track from beginning to end.


--Mac