It really depends on the position, but it can take some time, particularly for train crew and similar positions. If you are not going to get an interview, you won't hear back for months (or ever) - if you do hear they will e-mail you a form letter stating that the position was filled, or they decided not to fill it, etc. The process does take time, and they absolutely provide you with enough time to give two weeks notice (or occasionally more) before starting a new position, regardless of when you are hired. It's something that will come up in the interview process if you are called. Hope this helps and best of luck.