Unions are, and are intended to be, “adversarial” in their relationship with management. “Bargaining” is always adversarial to a degree.
So, if I want to have a business and hire people, I am in an “adversarial” position vis a vis my employees, no matter what my intentions are, and no matter how well we get along. it might be very mildly adversarial, or it might be seriously adversarial. But it’s still adversarial in its nature. If I’m dealing with a union, the workers are all banded together under some leader who supposedly speaks for them. That leader might or might not truly speak for them, but that’s the understaneding, and my relationship with those leaders is adversarial of its nature.
But if I want a business, I have to live with that, union or no union. If there’s no union, my employees’ ‘bargaining chip’ is working for me. I train them, lose money on them at first, teach them skills they can sell to others if they want to do that, and that’s part of the chance I take if I want to be in business. And the greater their skills, the more bargaining power they have relative to me. If I can’t live with that, I have a choice. I don’t have to start a business.
But in public employment, the “adversary” is necessarily the public. The public doesn’t choose to be in an adversarial relationship with workers. The relationship is the result (most of the time) in my being born in a particular place. Unlike a businessman, I don’t have the option of paying or not paying. I get imprisoned if i don’t. In that context, I think it’s different. Am I organized in the same sort of way management in a business is organized? Not at all, and I can’t be. Sometimes I am represented by people who hold my point of view, and sometimes I’m governed by people who are my “adversaries”; some of whom are beholding to public service unions. So, at times at least, there is no "adversary’ worthy of the name to the public service unions. I, and other like-minded citizens are powerless in the face of two “adversaries” in those circumstances. A good part of the time, MY representatives are actually on the other side, but I’m supposed to pay for the fact that, unlike a private businessman, I can’t bargain with anybody.
So, in my opinion, the usual “bargaining” talk people bring up when they talk about public service unions as if governmental units were Caterpillar or GM, doesn’t apply, particularly since Cat and GM can shut down or move offshore if they can’t live with the demands on the other side and can’t win the argument. Public service unions are a thing all their own, and the relationship between the workers and the public is different, since the public didn’t really volunteer for the adversarial role, is rarely a unified voice, and can’t opt out of “the deal” without going to prison.