Architect
It's a contractual thing. They were hired as DEC and DEFO onto the base pursuant to there being vacancies on the base.
Some, not all, will be accommodated on other bases (if vacancies exist), or offered HKG positions ON LOCAL TERMS. If neither is acceptable, then they will be terminated.
All of this, I might add, just 3 days AFTER bids for LHR closed. Nice.