TUS is junior in the RJ, no EMBs there. If you didn't get it right out of groundschool it would probably just be a month or two.
I believe most newhires will be going into the jet, though everything changes given timing and the company's need at that particular moment. Right now, we are getting a ton of new jets, and all the FO's that could transition (not seatlocked or senoir domicile-specific in their bid), already have, thus, newhires in the jet.
I think generally they would like to see newhires go into the EMB, and I would choose that myself so no one could transition in on top of me, but take whatever class they offer first.
Cheers.