The CV line is now operated by the New England Central, owned by G&W. G&W also more recently acquired the Providence & Worcester, which runs on the east side of the Thames. The two lines parallel each other up to Norwich then branch off their separate ways. Now, I have heard that traffic on the NECR is very sparse south of Norwich, with just a handful of customers and less-than-frequent service. But, the line is being upgraded with welded rail down to (I'm not sure how far south in CT). Could the NECR line support a passenger train up to Mohegan Sun given their current traffic levels? Probably. Would G&W (owners) be legit with it? Potentially. Would it make money? Most likely not. The line does pass right by Mohegan Sun, but not sure if its a "drop in a station and walk 200' into the casino" type of situation (most likely not). Since it would be a new startup, you'd most likely have to have a full length high level platform and NECR may want a second track (or a mini-high) in case of any high & wide movements. Given past experiences with "train to the casino", I wouldn't hold my breath on any service making much money. Look at Amtrak's Atlantic City service, and NJ Transit's ACES experiment. The buses seem to have a lock on casino traffic in the east. Mohegan Sun and New London are within close proximity and its a quick shot up Route 32 to I-395 to Route 2A to reach the casino.
Over the years, there has been talk of restoring passenger service from New London through Norwich and Worcester, and the NECR line in my opinion is a prime candidate for this service. You would have to rebuild the (what, 1/2 mile?) connection between the NECR and P&W lines in Norwich, but you wouldn't have to deal with crossing the Thames, nor would you have to run through the Sub Base. Since I don't think there are any customers on the P&W south of (is it still?) Dow Chemical at Allyn's Point (north of the base), you could, in theory, abandon that trackage and just reroute all traffic over to the NECR line. That'd make the Navy happy, I'm sure. And if you do a New London<->Worcester service, then you may want to try a platform at Mohegan Sun. Or market the station stop as "Mohegan-Pequot" to serve both casinos. But again, with the history of specialized casino services, yo wouldn't want to put all your eggs in that one basket. Instead, add it as an infill station for a larger project to develop passenger service to a corridor that lost it April 30, 1971.
EDIT:
It appears that that 1/2 mile or so connection in Norwich would require a new bridge over the Thames at some point. Looks like a "bike path" of some sorts exists where a bridge would cross the narrower part of the river, but you wouldn't have a direct connection given how close the NECR line is to the river. The switch would face north, so you'd have to go through the switch, then reverse to head north to the P&W. So maybe not that easy.
Also, a Google Maps image of the NECR line passing by Mohegan Sun makes the addition of a station "possible". It doesn't appear to be a steep grade change between the railroad and the "casino level".
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