The real power I think of a resident union isn't the the threat of strike. More that, it's more difficult for individual resident vs program conflict to get swept under the rug in various ways.
It provides a paper trail of collective resident complaints, potentially even in a way that is more anonymized across the group and hence more difficult to have any retaliatory or intimidating action against any individual.
(And before anyone says, that doesn't happen very often, I will say I've definitely seen it more than once, even at very nice and not malignant programs. Multiple reports across multiple residents, the vast majority of whom were never even in any hot water themselves.
Sometimes programs don't even perceive that what they are doing is singling anyone out and retaliating in the pressure they apply or things they say.
"Oh, you want time off for this assault/insert other trauma/illness you endured? Well, we can do that, but I think then we will have to consider what we report about your professionalism..." Many residents back down in convos like this.
You think I'm lying or making this stuff up, but I'm not. I've heard it from enough horse's mouths, and especially within a small program, that the odds ALL the residents (including the ones on the good side of the program) are lying/exaggerating, is very, very low. Seniors will see the patterns being there long enough as well, in addition to individual report.
Anyway, besides making it harder to pressure any individual, the way that unions and programs negotiations tend to occur, makes there be an official paper trail of complaints and well as responses. This can also allow there to be pressure from the community or PR on a program as well.
Lastly, is that a union can retain legal services to assist them. As is ALWAYS stated on this board, and has never really been seriously refuted and thus has been essentially treated as a stated fact, is that when an individual resident lawyers up this tends to increase the antagonism between resident and program (and I discuss elsewhere why in some considered cases this is still worth doing at times). A union can have legal representation.
So it doesn't have to come down to threat of strike specifically, for how a union and its concerns might be somewhat harder for a program to dismiss, and they have to come to the negotiating table as a result. Certain tricks a program might use to get their way simply will not be possible. How they handle the complaints will be recorded and reviewable by outside parties. There is more transparency and accountability.
How do I know? I know some of the inside dirt under the system without representation. And then I have also tried to follow cases where conflict occurred between a resident union and the program and the outcome. Of course only when it makes the news. Which, it does. Another power of having the union.
(Individual resident/program conflict can make the news, but even in cases where the program looks very bad, there is no happy ending for the resident. And agreed, most cases that make the news tends to look very bad for the resident many times. I have a theory why this is (when residents do have a very good case and the program is very wrong, the programs take steps to settle just so it does stay quiet out of the news). Anyway, by the time individual resident/program conflict makes the news, nothing good usually comes of it. In contrast to when resident union/program conflict comes to light. These things may not go the way unions want, and even individuals may still be damaged, however, it's not necessarily a given with a union involved like it effectively is when it's only one resident).
That said, typically the union is very limited in what concessions they are able to get. This is, because as pointed out, strikes are not a terribly useful tool for the resident union. Also, because residents as a class of trainee/employee, are basically in a legal no-man's land when it comes to protections that typically apply to standard education systems/students, or employees in the workplace. Residencies are literally exempt for much of the law that would otherwise apply to other classes of individual. This limits how much is even on the table for residents to negotiate for.
Now, no doubt standard treatment of individuals on the part of the program is still possible even with resident unions in place. They can only do so much to advocate for individuals.
However, if there is actual abuse and it does apply broad across the board, I fail to see how any group of residents can get any concerns addressed whatsoever, without a union, even one that doesn't threaten to strike.
No one wants to make training last longer. I don't know enough to know if it makes a difference to program standing under the ACGME, if, for example, residents walk out of all educational activities like seminars and morning/noon report. I know these activities and their attendance in some measure are required by ACGME for a program's accreditation. In this sense, residents could perhaps "walk out" without not caring for patients. Missing days inpatient/outpatient is what always must be made up and can only be made up when needed to be made up, by training extension. Obviously this affects the education of the residents, and program standing which threatens their career, however I would think remedy might come without having to extend training time. And it may put pressure on a program to address resident concerns before the issue actually threatens accreditation.
I haven't followed resident union/program conflict enough to know exactly what, if any strategies they have besides strike or increased transparency/PR at their disposal.
In any case, it seems that the resident union is better for bargaining for better treatment than no union. But no, they are not typically going to get anything with a strike. And no, they are not going to be able to bargain for unicorns and rainbows. And some individuals will still get spanked/abused in any case. The only thing I can see, is it's better than nothing. Grievances get recorded and airtime. Hopefully the hospital/HR/PR/legal risk management puts pressure on the program to address concerns where they can.
I know the power legal risk management, the lawyers that work for the hospital, have in getting hospitals, admin, programs to do things they don't even want to do. It's just the way it is. The lawyers always win. And that's even when it's a single resident and the program operating in the shadows. So I would venture that a resident union can apply at least some pressure.