Or the workers could slowdown if they can't afford to quit. E.g. the workers could say that train cars are going to be limited to X in length and a sympathetic worker would just detach any cars past X. So long as the workers had enough solidarity to pull off doing this anonymously - or similar acts of resistance, I don't see how this would fail to solve the problem.

The workers could decide to stop doing precision train scheduling (or whatever it was called). They could force their employer to give them concessions. If you're saying the workers can't afford to quit or resist then you're saying they have to accept whatever they are given.