It is not legal. There are no CT state owned property's that are legal for jeeps. If it is a powerline trail then it is either state owned or the state owns the rights to the land. Either way, not legal.
Ct has some dirt bike trails and snowmobile trails. Nothing state owned that is legal for four wheeled vehicles. There is private land that is legal. You still need to have written permission from the land owner on you at all times. Otherwise you can still be ticketed.
That bring said there are some spots that the cops more are less look the other way. Just behave with respect. Don't speed around, there ARE hikers in there. Don't litter! If the park closes at dusk, be gone by dusk. They will sit there and wait for you to come out and ticket you. Don't harm the plant or animal life.
All in all. Much safer to wheel on private land with permission.
Not to mention illegal wheeling makes it much harder to get legal spots set up. Most hardcore wheelers will get upset with you for wheeling illegal spots. (Rightfully, in my opinion)
If you google it. There are wildlife clubs that are anti wheeling and encourage their members to report any illegal wheeling to the police and their own data bases. They use this information to make it harder for us to wheel. They collect all kinds of info. Entrances, license plates, vehicle types. None of it good for us. I don't like giving them more ammo.
Of course I have been known to go where I shouldn't from time to time. So don't take any of this as preaching.