Near as I can tell BIAB uses 120 ticks per quarter note and since there doesn't seem to be a way to use anything other than a quarter note for a beat then:

ms/beat = 60,000/bpm

ms/tick = (ms/beat) / 120

So for 4/4 time at 100 bpm that would be 600 ms/beat and 5 ms/tick. I hope that's correct.

Russ