The "best" part about the Cog in the winter is that the accessible ski terrain consists only of the land next to the tracks. This will be the first winter, and should be an interesting experiment. Hopefully, it doesn't continue.
As far as plowing on Mt. Clinton Rd, a portion of the road is used as an important connection for the Great Glen to Bretton Woods Ski Marathon. It's the best connection to the Bretton Woods nordic system. It might also be a part of their nordic trail system all winter. Two years ago the connection was the Base Road, which had a large of number of very fast moving snowmobiles on it...not safe, and fairly scary. Skiing 50k is hard enough without snowmobiles barrelling at you at 45mph.