Re: busway
Yes, if there is the space required by 312.8 you can use one of these as a raceway.
Take a look at 312.8 (2002) just make sure you read the whole thing, the first sentence says no, the rest says yes.
I have not found busway switches to have enough room to work the conductors that have to be in there, I would plan on running both to a common J-Box and go from there out to the loads.
Don't forget about derating the conductors 80% as you will have six current carrying conductors in one raceway.