If your implication is that the crew might let you do something outside of official policy, the problem is, what if a different person is working that day?

And how would you even know what the usual person would allow on a train you don't usually take?

Sure, if you're stranded it doesn't hurt to ask. But it also doesn't hurt to see if you can buy a ticket for yourself and your bike, even just minutes before the train arrives.

In either case the worst outcome is that you can't.