Eventually the Plugin should a decimal point tempo map like RealBand to follow a live DAW recorded session.
But for now if you have Biab songs with tempo changes and open them in the Plugin you just simply need to drag a midi track or real chart (generate any midi track if not there) out of the Plugin into the DAW and this will give you you tempo changes.
The Plugin should soon have a Midi drag export button that will give the DAW time signature changes, tempo map, midi chord markers and midi chords.
Likewise it will have a midi drop button to import these from the DAW.
Along with associated File > Import/Export function.