Nobody knows...
It's up to Skywest. As far as the MOU between Alpa and CAL is concerned, you have to go back. If Skywest offers you the opportunity to stay (based on an interview, personality test, shoe size, whatever they choose) you could then choose to resign your Coex seniority. Will Skywest do this? Some responses on this board seem to suggest that they may. I personally hope they will at least consider it. However, don't expect to hear anything official about it from the union since their official position is clearly stated in the MOU. Additionally, they probably wouldn't encourage you to leave for Skywest since you would then be without union representation. Oh the irony... "I'd like to thank my union, ALPA, for getting me this great job with Skywest. Now that I've got it, I'll be resigning from Coex!"