I'm a Mesa EMB capt in CLT, and here's the story as I know it - no garantee of accuracy though.
After 9- 11 we furloughed about 315 guys, and to date have recalled about 200. I think the majority of guys that are still on the street are AMW (Air MIdwest) 1900 drivers, but there are a few RJ and Dash guys too. You can bid from certificate to certificate ( common seniority list) I think that some of the guys that were recalled had to be retrained in either the ERJ or the 1900, since we are fat on CRJ and Dash 8 guys. We took delivery of 5 ERJ's since 9-11 for a total of 25 now, and the rest of our 36 a/c order is up in the air right now while mainline sorts out the scope issue.
Prior to 9-11 upgrades were at rediculously junior levels....12 to 18 months for ERJ capts and you could concievably even get hired as a street capt in the 1900....obviously that has slowed down. now its taking 4yrs plus to hold ERJ capt and way more than that to get CRJ capt. AS long as you met ATp mins you could get the upgrade, but I think that has changed as well
Hope this helps