This is one of two places that are easily visible on the same train. Taking a train from Penn station in NYC to Buffalo will give you the opportunity to see the arsenal, then many miles away near the trip's end (or beginning if leaving buffalo from exchange st. i believe), Buffalo Central Terminal.

Not sure on security, but it seems that the yard's accessible (albeit dangerously) on a small boat.
If you look carefully, you can find it on aerial map websites. Some people have directly named it.