This will be an interview with most likely 2 managers, one will ask the questions the other will be busy writing and may chip in when they feel like it.
Do some research into the company such as routes they travel, The MD's name, parent company etc. find out something interesting about the company to talk about, anything will do to show you've at least looked at their website. Have a good reason for wanting to be a train driver and be prepared to explain that in detail.
You will be asked about previous experience of working alone,multitasking,decision making,dealing with emergencies etc.
They are not looking for a train expert, more someone who is aware that safety is your first concern and you have the ability to get through the training to their standards.