In July when I had an interview with BNSF they asked me if I had any questions. I asked"What's the best thing about working for this company." They told me it was a great question and spent a good ten minutes talking about it
Ask about your seniority district, and what you will have to cover. How big is the district, and what are the likelihood of being shipped to an outlying point. Ask about benefits, insurance, 401k, Railroad Retirement, and private pensions.
Often they will include an operating supervisor, like a trainmaster, in the interview. You can ask about the jobs that you will cover, and their challenges.