Interviews can vary depending on the role you have applied for, so the best thing to do is look up the competencies for the role you are after and think of some examples in which you have demonstrated them in the past.
You will probably be asked questions in the form of, 'Give us an example of a time when you...'.
When asked questions in that format, try and provide your answers in the
'STAR' format. This stands for:
Situation (What was happening?)
Task (What was you expected to do?)
Action (What did you do to resolve the situation?)
Result (What was the outcome of the situation?)
You should demonstrate a passion for the role you have applied for and of course the railway, but try to avoid coming across as too much of a rail enthusiast, as you may create the impression that you may not be totally focused on the task at hand.
Also, do plenty of research on the company you have applied for.
Good luck!