You're right that I wouldn't recognise an unknown word/phrase, but since train announcements are operating in a limited context and I'd be seeing people respond by getting off the train at multiple stops you'd hope I'd figure it out before too long.

This is of course assuming I know some of the language and can recognise basic words such as their equivalent of passengers, going in completely blind would be a real mission (just as it would be coming here with absolutely no English).