We've had a bunch of design your own mountain threads, but what about designing a new ski train (e.g The Old North Conway train has been done, or the Sunday River Narrow already exists). Here are the some guidelines
Try and use existing track, though if you need to take land by eminent domain, you need to justify it
You need to start from a population center, stops on the way are OK, remember, you want to make a profit on this RR.
You need to end up within 20 miles of your mountain, more points for being closer
Optional: Ticket Prices
There's no waiting for friends on a powder day.
A rail link is more doable for Sunday River than most places. The Atlantic and St. Lawrence track is in pretty good shape and runs through Bethel, what about 5-6 miles from the base areas? Tracks run to Portland, but linking with the Downeaster is a problem. Those tracks cross at Danville Jct. outside Auburn (Lewiston).
Okemo is already well positioned for the return of the ski train. Both base areas lie within a few hundred yards of an active Amtrak rail line, in fact there's already an existing Amtrak station in Ludlow.
"Freedom often leads, but responsibility always follows close behind."
If NJ transit ever opens up a section of track that they call the lackawana spur you could have a legit ski train. Taking the Midtown Direct from Penn Station you could access Shawnee Mountain, Alpine Mountain Camelback, and Sno Mountain(Montage). There has been alot of talk about opening this section to relieve some of the congestion on I-80 in NJ. Of course there is the anti-anything crowd in NJ so chances are just as good it will never happen.
There is no amtrak station in Ludlow. The Green Mountain runs their tourist excursions there in the fall, and their freight obviously year round, but that's about it. They could run something from there southeast to Bellows Falls, where there is an Amtrak station (a Vermonter stop). I don't see this as viable though... Up in Maine, the Mountain Division that went by the base of Attitash splits from the rest of civilization in Portland (right at the Downeaster station basically). Might be able to do something there.
Josh brought up a good point on another thread: ski buses are generally successful.
However I don't think it's because of free parking at the bus stop... parking at train stations around Boston is in the $1-$3 range, I doubt that would be a major deterrent to ski trains. Here's what I think would be critical:
-- Start from a population center, but also have suburban access. There's more parking and families with little kids. E.g., if you're starting from Boston have a stop around 128 and/or 495.
-- Serve multiple areas. I think the major reason buses work is they take you right to the mountain. Having to change from train to shuttle bus on arrival is probably the biggest negative. You could overcome this by offering a choice of destination -- ideally a town with several mountains nearby.
-- Schedule some flexibility. Weekend trips are probably the best bet... but Amtrak's Cape Codder used to give several day options, like to the Cape Thurs/Fri/Sat and back to NYC Sat/Sun/Mon. That way you're not locked into Friday PM-Sunday PM. (Although personally I avoid the 'usual' weekend trip times because I hate traffic, which would not be an issue with a train.)
One of the biggest problems in mass transit is the last mile to the destination. It's Ok if you are walking, but a problem if you are carrying anything. Take a look at the Newburyport MA train station to see what I mean. Considering the amount of equipment that a family with children might bring with them to ski for a day, I think the train stop has to be right at the ski area. I know if I had to transfer equipment from my car to a train, train to a shuttle bus, shuttle bus to the base lodge, I don't think I would do it.
In a sense a modern bus is a ski train with a lot more flexibility. And a full bus gets very good person-miles/gallon.