If you generated in BiaB originally using one of the odd time styles in BiaB, it doesn't actually do 5/4.
It divides the 4/4/ bar into 5 beats. Sounds weird, but here is the difference.

In 4/4 at tempo of 120 each beat is 500 ms (if memory is right). 500ms X 4 beats = 2000ms
So that same 2000 ms is now divided into 5 beats, which means each beat is now actually 400 ms

Using my handy dandy music tempo/time calculator program (that I made myself by the way)
400 ms = tempo of 150

When you open the BiaB song in RB and change it to 5/4 time, try changing the tempo to 150 and see if things line up.
It doesn't make any sense, but see if it works.. you're just trying to make the bars line up to the actual time divisions.

I do not work here, but the benefits are still awesome
Make your sound your own!