For those that can and do actually read...This is not a Union thing; never has been. The company, and its parent company, decide when, where, how, for whom, what contracts, jets go here, jets go there. Unions <plural> are not invited into the meeting rooms for those discussions.
N798AX is a -200 who has reached a cycle limit. The aircraft either has to have expensive maintenance performed or be scrapped. With today's market there isn't a viable option for the a/c at this time; therefore it will be taken out of service and most likely scrapped for parts and beer cans. If it gets replaced, the decision will be made from above (although it's not anticipated to be..).