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.

of course once BIAB plugin has the option and ability to stream audio in real-time from the BBM4 engine directly - and the BBM4 engine does the time-stretching in real-time to the generated audio held in RAM ( as BIAB standalone does ) we should be able to have the plugin playback follow the tempo of the DAW directly.

This of course is where one would ideally like to get to. This is how BIAB standalone works. It is fast at generating because it generates straight into RAM and not onto disk. And we can of course adjust tempos on the fly.

All this needs to be brought into the plugin and BBM4 version asap.

I know i'm biased but rather than doing a separate Rewire implementation with all the hassles that entails - i'd much rather have PG focus on making the plugin the standard way we pipe audio into a DAW in real time. There are so many advantages with a plugin based workflow.