The likelyhood of a train going from Medfield Junction through Dover is exactly zero.
It's also pretty disingenuous to claim that it connects to the Needham Line.
MassDOT concluded that acquiring this rail asset supports our goals of increasing use of freight rail, which takes trucks off our highways and reduces greenhouse gases by consolidating the movement of freight
This from the same agency that essentially kicked CSX out of Beacon Park, requiring more trucks on the Mass Pike east of Worcester?
Literal zero...it's officially abandoned now. I don't think the switch has been spiked since it ties into the storage siding/runaround on the Framingham Sec. and the portion of the line several hundred feet up to the Ice House Rd. grade crossing is still completely fine for MOW storage use. MassDOT is obligated in the deal to do some freight-related track upgrades (though obviously at no rush). So there will be things like crossing surface renewal, tie replacement, some stick rail replacement, and whatnot. Most of the crossings are flashers-only, so they'd probably also be installing gates at several of them...especially in Game Train territory. Couple southside crews will probably eventually get qualified on the Upper Secondary as provision for equipment moves in a pinch between Franklin and Worcester Lines. Much like the Hospital Train route up north it's useful to have in an emergency.
It is a consequential freight line. Small business, but at least 3 dailies make round trips down it with some additional run-as-directeds. And with Massport hellbent on generating more port freight at South Boston, Fall River, and New Bedford it's the last rail link on those routes that the state doesn't control ownership on for being the initiating party on upgrades to support the pipeline to port freight (as debateable as that initiative is). 286K loading weight on the line currently extends only as far south of Framingham as Medfield Jct. Per the State Rail Plan they want to start chipping away at it to get further down. It would only be 5 additional miles of uprate to get to Walpole Yard. Then the Foxboro commuter rail upgrades would two-birds-for-one-stone the 286K job to Mansfield Jct. The NEC is already 286K-rated Mansfield-Attleboro Jct. And then they have eventual plans (more dubious, perhaps, but possibly bootstrappable onto a Cape Codder or Providence-flank Cape Flyer track project) of doing the same on the Middleboro Secondary to Taunton because South Coast Rail would uprate the FR/NB branches to the ports. You'd of course be talking itty-bitty investments tied to no particular schedule, but there is a long-term freight logic to it.
That's part of the reason why the MassDOT mothership was the one that made the transaction, and not the MBTA. I would imagine if Foxboro happens there'll be a paper transaction to transfer ownership or lease control of the Walpole-Mansfield segment to the T. But the purchase itself and the long-term control of the Upper Sec. was a MassDOT joint. The T budget is not taking any hit for this, and much like the Knowledge Corridor to the extent the T track dept. is borrowed for engineering and maintenance they're on a 1:1 cost reimbursement for the extracurricular. But important to note that this does NOT directly affect T finances.