We got a response from Volition in the thread Ange1 posted.. turns out all tracking and such is actually done as markers in the music file. The catch is it may be hardcoded in, or it may be doable when we do our own music files.. so we'll have to see that.
If it IS easily moddable, it means any music you use you'll have to do all the music triggers (wubs, beats, etc) by hand for it. So, Dragonforce is doable, but it'll be a pain to do. On the other hand, it does mean you can throw tracking to the wind and just cram it full of beats to make it rapid-fire...