You get to bid on the first day of training depending on what the company needs at the time, It might be an all CRJ class split between ORD and IAD. Or an all 328 class split between LGA, BOS, CVG and IAD. there has been a few J41 classes lately due to the Dornier situation.
One of the latest Doh-Jet classes just got placed in CVG. If you get the 328, chances are you might get put there. My guess is not too many people want to be there and as a new base for ACA they have to fill it with about 40 crewmembers. As far as asking for it, I don't think your input would change staffing needs.