I'm approaching this from a non-rail background and just commenting on phone interviews in general....
I've had a couple with firms for an internship, and one thing I did was dress smartly, even though I obviously wasn't going to be seen by the interviewer and was just sat in my room at my desk. That way it helped to me remain formal and not slip into colloquialisms such as 'you know'.
This may not be at all what you're after, in which case feel free to ignore!
Good luck.