Agreed, those cars might be better off where they are for the most part. The aftermath of prior taggings has been a good, thorough, and well needed clean and wash - something that unfortunately is otherwise not a regular occurrence.
Ideally the T would run 3295 on occasion. It has a pantograph, and last I knew no enormous structural or electrical issues, or at least none that some TLC in Riverside shop couldn't address. It would no longer be able to operate north of Government Center, unless the track configuration at Inner Belt Yard includes a loop (I think it does?) that could be used to turn from Lechmere. But the MBTA seems to have very little interest in charter operations nowadays, so it is highly unlikely.
5734 has some major structural problems (not just the roof) and cannot run unless serious money is spent on it, which is unlikely. I've sometimes wondered if the mechanical components (motors, trucks, controllers, etc) should be returned to Seashore and then body can be "stuffed and mounted" on dummy trucks in the atrium of the State Transportation Building, like SEPTA did with the PCC in the basement of 1234 Market. Equally doubtful though.
Interestingly, if the 5734 were structurally and mechanically "up to it", it is technically possible to operate that car with a pole on the Green Line today, despite the reconfiguration of overhead wire to accommodate pantographs and the elimination of wire frogs at junctions. It requires no more ingenuity than an open rear vestibule window and a second employee (one with a good eye and a steady hand on the retriever rope) to pull the pole approaching wire junctions, let the car coast underneath, and then raise the pole back up to the wire. If the guy on the rope is an expert, you don't even need to stop! I know this is possible since I saw it in action while riding on one of 5734's last private charters in 1991.