How it is now using the BB .SGU format it only stores tempo for each bar not for each beat and it rounds the tempo to a whole number, it has not got real time signatures other than 3/4 4/4 and only 255 bars. RealBand has real time signatures and decimal tempo maps and it's own file format .SEQ and more than 255 bars.
It needs fixing to be able to play back the already generated tracks to the tempo map so if the tempo is changed in the DAW then it will play back the already generated tracks to that change so if you are using ACID render that will automatically fit the DAW track when dragged in, if you are not using ACID in you DAW then you can re-generate to the new tempo map. Once the play from RAM is implemented this will be a lot easier and quicker.