New hires are not seat or equipment locked as of now anyway. This is only partially true though to the extent that the company has no written policy to that effect.
Practically speaking, the last year or so has seen many new hires languishing at the lower pay scale a bit longer than they would like due largely to the company not offering transition opportunities or if they got the award, they were bypassed for training. That trend seems to have abated a bit and most of the backlog of guys with awards are moving on to class now. That said, new hires are still being hired into the jet making fewer opportunities for the old timers to slide over. On the other hand, there is a way to receive the higher pay while still flying the 120 if bypassed. I'm not up on the details of that program, but it is happening.
Yes, if you are initially assigned to the E120, you can be bypassed for the CRJ upgrade, but the company must pay protect you.
There is disagreement between the pilot group and management about how many pilots can be pay protected. The pilots feel that any time a junior pilot gets a bid you should hold by seniority, then the company must pay. Management feels that they should only have to pay protect the number of pilots who were bypassed for an opening.
My suggestion would be to immediately bid what you want to hold, all the way up to the CRJ700 Capt slot. If you find yourself in a good place and do not want to give up your aircraft, or schedule, you can always pull out your bid and select something else.
I was held on the E120 for six months and got paid for the CRJ for five of those months. If you fly your butt off, you can make around $40K the second year and $45K the third. (Counting per diem)
Right now upgrade to CRJ Capt in DFW is about three years and four for ATL. The ATR is about 2 and 1/2 for ATL. Either aircraft pays the same. I'm guessing between $53 and $55K on reserve for a third year CA.
There was also a captain in the 600's who got the preliminary award as well. I am not sure if it stuck on the finals, but if it did he better marry a crew scheduler or become Willie's best friend, because he will be on reserve FOREVER.
Actually, with the hundreds of hours that they will rack up in the first 6 years, they should be ready to move on to a major when they start hiring again. Personally, I wouldn't sign anything over 5 years.