Not really, especially if what the employee specialises in is very specific to that job and they would have to retrain to get a job with anyone else, not to mention it probably being very difficult to get one. Since London Underground unsurprisingly have a monopoly on the job of London Underground ticket office staff, it would probably have to get *really* bad for them to quit. I think it's perfectly reasonable for them to strike to try to change something that's bad, but not bad enough for them to go through the pain of trying to find a new job in this economy and retraining for it. If we were talking about TOC ticket offices, you might have a point since it would be much easier to work for a different TOC largely retaining the same training given it's all the same ticketing system (I expect - correct me if I'm wrong), but even then the pattern is still getting rid of ticket office staff rather than hiring new ones as far as I can tell so it would still be rather hard to find a new job in such circumstances. So, again, I would advocate striking here.