Until several years ago it was informally termed collective begging, as we really had no recourse if we did not agree with the offer from the employer. We could seek arbitration, but in the end it was up to them to fund it, or just do as they like. Public support campaigns were the only other alternative, (although active negotiations are prohibited from disclosure.)
We do have binding arbitration now, where if no agreement is reached the packages go to a independent arbiter who selects one package as a whole. It's all of this or all of that system deliberately designed to try to force agreement at the table or reasonable offers if it goes to arbitration. If you reach too far, you grant a win to the other party and they get their whole package.
As far as how we got the arbitration, it was done as a referendum amending our County Charter with about a 4 to 1 approval among the voters.