If he hasn’t been dismissed due to his behaviour, or been convicted criminally, there’s no way of finding out really. Reference checks are usually so vague l as in; “Did he turns up to work” or, “how many days sick has he had in the past XYZ amount of time”.
Even if someone had been dismissed, the reason wouldn’t be disclosed on a reference.
TOCs also don’t much like to talk about attendance/timekeeping records these days (lots of days off sick might be due to a disability etc.) .
As with most employees, a standard HR reference listing job title, dates of employment (plus safety of the line form) is all that is generally supplied.*
I don’t really understand the OP’s question. If you’d been a bit curt to a passenger, or conducted yourself unprofessionally (we’ve all had days like that!), why would you volunteer it? A job interview is your shop window to sell yourself!
On the other hand an “altercation” with a passenger could be turned into a positive example of “dealing calmly with an irate customer... [insert HR friendly waffle]....” in a competency type interview.
*although the railway is a very, very small world so there’s always the possibility they will find out through unofficial channels. Nothing can stop a manager putting a call in to their mate who works in the prospective employee’s depot (“what’s Joe Bloggs like?”).
Job done!