Reminds me of air traffic controller strike https://en.m.wikipedia.org/wiki/Professional_Air_Traffic_Con.... If anyone think they are not replaceable they are in for a rude shock. City can easily hire private security/bring in the guard/hire new officers/reassign officers in desk jobs.
Except that police union contracts tend to be somewhat more constraining than the ATC contract, and municipalities don't have the power of the federal executive branch to back them up for capriciously terminating employees.