Caution second hand info. I had lunch with a reservist who was ex CX, and we started discussing this very situation. He was activated for OEF, and since CX has US bases they have to abide by USERA. The catch, according to EX-CX pilot, is that CX has a very long memory and it doesn't take much to get on their bad side. So instead of risking a failed check ride or long upgrade he resigned. He did say he enjoyed working for them, and they were a very professional organization. Go to pprune if you want to understand CX's corporate culture, and his unwillingness to upset them.