There was a train derailment many years ago, and the wreck is still there. The forum poster known as Winnipesaukee Divers can give some first-hand information -- something was posted here within the past two years, as I had inquired about the wreck. Seems there's not much left -- lots and lots of rusty metal. I seem to remember that it didn't sound like much of a dive.
Re: The Witches -- No idea. Never dove there, and haven't seen it listed among the popular dive sites on the Lake. That being said, there are plenty of great sites that aren't on those lists -- just depends what you like. Give me some old bottles and some big rocks, and I'm a happy guy.