ALPA was trying to push for FFD (Fee For Departure) agreement between carriers. It was initiated to reduce the whipsawing between airlines.
In a perfect world if your airplanes went flying elsewhere, the pilots would go along with them.
PSA's management was for this as well. It meant that they could get current qualified pilots at year 1 pay.
Alpa would give them seniority at the other airline but would start at year 1 pay. Either Captain or F/O.

So ALPA would be happy protecting pilots. They would lose income because of the year 1 pay but they would still get some.
Company is happy because they are getting year 1 captains.

I personally don't think this is fair. If people work at Mesa, they have the job security of working for Delta, US Airways, United...
Where as if you are a wholly owned you have only one airline.

Even if Mesa pilots went to another airline to work flying the same airplanes they would still have to start from scratch from a training point of view.
One of the reasons why Mesa is going out of business is because J.O. is not a person who has great leadership skills.
He treated people like crap, took advantage of them and look where it got the company.