For us users working a lot with Midi Files and Karaoke Files, it's a HUGE drawback that BiaB can't read the BPM track in Midifiles.. So PLEASE PG Music, implement it...
This is a midi tempo map in RealBand on the right, on the left is the Biab tempo map of it, so it takes the average over the bar and rounds it. If you just have midi with tempo changes like 120 to 130 then back to 120 it will work best.
And of course, BIAB only does tempo changes on a barline basis, whereas RealBand supports tempo changes anywhere along the time line. BIAB also only uses whole number tempos (so it rounds from the fractional tempo), whereas RealBand supports fractional tempos. It's been that way for a long time (not saying it should stay that way, just pointing out that it is expected behavior).