Union (apparently) is force transferring me and 5-7 other lower seniority drivers from my center to a different in-hub center due to their staffing issues

Is this allowed? Would this not count as a loan? What about Saturdays? This would really screw over my current center’s Saturdays, as we haven’t finalized the schedules yet and are still trying to get 6-8 volunteers to fill in saturday routes because we’re short staffed on them.

We just found out about it yesterday, and our Shop Stewards are fighting the union on it.