My understanding is XJT's contract has a provision that large-RJ rates can be decided by an arbitrator if negotiations aren't fruitful. In light of the recently signed regional contracts (e.g., Pinnacle), the company probably thought an arbitrator would be friendly to their cause.

So the XJT'ers wouldn't necessarily volunteer to undercut ASA. But they decided to ignore the TPA they signed and exclude the ASA MEC from the closed-door negotiations. So there's that.