Not to rain on the Mesa bashing parade, but to answer your question...yes, major airlines do indeed hire Mesa pilots. In fact, for example, there's a very sizeable ex-Mesa group at SWA that I personally know of. As a Mesa pilot, I jumpseat on AA and UA, and have run into more than a fair share of ex-Mesa pilots as I shake hands to those in the cockpit.
PIC time is PIC time, whether the A/C is operated by Mesa, SkyWest, ExpressJet, etc, etc, etc. As we all heard when we were doing our primary training, "it doesn't matter where you get your licenses and ratings, just so long as you have them". Same thing applies to PIC time.
As far as the "scabs" you're referring to, Freedom A, I would hope that no major, nor any other airline, employs those individuals. I know of one Freedom A scab that went on to Fed Ex, but that's hopefully an isolated incident. So, in aswer to your question: the majors do indeed hire Mesa pilots, yet the majors have not been hiring Freedom A pilots.
I chose Mesa due to my personal goals in this business...particularly, to get on with SWA. Whether or not I succeed in achieving that goal remains to be seen. Three of my mentors at SWA (all ex-Mesa pilots) urged me to consider Mesa for the prospects of a relatively quick upgrade, getting 1000 PIC, and applying to SWA. In one of these mentors words, "if you go to the best regional out there, no one wants to leave, and that just puts you in the right seat longer". Makes sense to me.
I'll never be the one to defend Mesa (although it appears I'm doing so). I looked into practically every regional carrier in my job search, so I'm familiar with others' contracts, and how their pay, QOL, etc differs from Mesa. Obviously, Mesa is on the low end of most variables (such as pay, days off, etc) but it's really not as much as people like to make it out to be.
I didn't come to Mesa to be rich, nor did I come here to make Mesa my career stop. If I was concerned with money, I would have never left my corporate world job. Even the highest paid regional would have been close to a 75% pay cut for me. So, I really didn't see a whole lot of difference between $21 p/h first year pay at Mesa, versus whatever it is at Comair or ExpressJet. And although it would be nice to have more days off, I live with what I get. Considering I was lucky to have 3-4 days off per month when I was working in the corporate world, 13-15 days off per month here is tolerable. I sat 3 weeks on reserve when I first started, and have been a lineholder even since. A lot of the horror related to Mesa comes from being on reserve, and I have been fortunate to limit that experience.
I hope Mesa pilots stand up for themsleves in 2006 when the contract is ammendable. Trust me, there are a lot of upset pilots here, and are salivating at the opportunity to make up for what was accepted during the last round. Hopefully, there won't be another Freedom fiasco to deal with either.
Feel free to bash Mesa....I'm certainly not going to stop you. This isn't the perfect place (FAR from it) but what regional out there really is right now?