Don't do something embarrassing if you want to be saved embarrassment. If you're closing a branch office, but providing the option for people to move to SF, that's important information future candidates should know about how your business operates.
More broadly, it pays to know your rights as an employee.
toomuchtodo and I both spend too much time on HN and I've gotten to know him a bit from his posts; I ascertain he's probably pretty far left of me, politically. I'm more of a stereotypical tech guy, left/center-moderate, but even I agree, employees have rights, and it pays to know yours. Your employer cannot fire you for bargaining collectively. Period. IANAL, but my understanding is that the FLSA specifically protects what you're doing now, and you might even be able to file a wrongful termination suit if they act on it. It also means the language in whatever agreement you have might not be enforceable.
I grew up in Chicago and know union excesses well. But whatever your ideology, it pays to know a bit about the law, and what you can and can't do.
[1] https://www.dol.gov/Olms/regs/compliance/EmployeeRightsPoste...