generally unions are hierarchically structured so that one smaller union can call on the resources of their parent organisation. my employer has a collective bargaining agreement with a union representing “white-collar workers” (it’s a more formal term here), which is itself a sub-union of the “central organization for professionals” which means that the sub-union sets the minimum terms and if the company fails to uphold them they get struck by all the sub-unions of the central org. since my employer is active all over europe, this may eventually escalate to the EUTC if bad enough, meaning the company would be seeing strikes all over the continent.
CBA’s occasionally get renegotiated based on directive from the central organisations. this includes minimum yearly raises and such. currently we’re just coming out of a negotiation period where raises were centrally agreed to 4.5% over two years, which together with inflation being higher than normal meant that most people’s actual salaries went down. however, this was not a surprise, it came as a request from the central bank as a means to lower inflation back to normal, which to their credit seems to have worked. so in the short run it was a bit anti-worker, but it stabilised the industry which means i still have a job. my previous employer did not have a CBA, with the reasoning that their terms were better anyway (and they were but the point is is the “collective” part, not the “agreement” part) and when inflation hit them they basically randomly stopped giving raises. a few of my colleagues actually passed me in salary.
as for another pretty interesting example, the tesla thing. the strike they are currently facing is due to them being non-union. there is no rule saying they have to be, but in general auto makers are unionised. tesla has a standing policy to not talk to unions, and they are not doing anything wrong on paper, so the union is basically besieging them. people working for tesla generally don’t want to be unionised (at least they say so publicly) so the strike is based on other unionised workforces (like electricians, postal workers, dock workers) refusing to do work for tesla. tesla are calling this behavior into question, and on paper it is questionable. it has prevented a lot of shit historically, so they won’t get anywhere with it, but looking in from the outside it must seem a bit odd.
personally, i would add a third item to that list.