SNCF rules are quite clear on the matter - if you take pictures for a strictly private use and without selling them afterwards, you have the absolute right to photograph and video anything you want as long as you are somewhere that is open to the public, without needing any official authorisation.
Something important though: if you happen to have the face of an employee (or anyone for that matter) in one of your pictures, and that person asks you to delete that picture for whatever reason, you absolutely have to delete said picture.
Station staff usually don’t really care about your camera. Driving staff either, and there are more drivers who would actually give you a friendly wave than drivers that would flip you the bird, hide their face, or actually bother you.
