Honestly I'm not 100% sure. For context I'm in a much smaller union for a different essential service. Decades ago we (not me personally, I was a kid) were legislated back to work and the arbitrator decided to slip in a binding arbitration clause to our contract. The point is, we aren't allowed to strike and from my understanding of an illegal strike there could be fines for the union, fines for the members striking, and possibly jail time for union leadership. Obviously they could likely fire everyone with cause, but that would be a terrible decision when they're already struggling with retention of qualified people. Everyone could decide to quit at the same time, it's not a strike if you aren't employed, but that won't really help anyone, especially if you have specialized skills. In this case you can't really just go get a job as a railway engineer somewhere else.

Maybe check back with me in 2026, depending if our relationship with management gets better or worse I might have some more relevant first hand experience.