Oh, Millis was always for it bigtime. They're the ones who get screwed here. And Medfield was indifferent more than it was opposed thanks to the presence of the always-active Framingham Secondary still keeping their future passenger options in-hand (with potentially better station placement than Medfield Jct.). They just didn't see the urgency. Needham is pro-rail, but simply didn't have any skin in the game because they have service at Needham Jct. and the last restoration proposal wouldn't have restored the tiny pre-'67 Charles River intermediate stop way out in the woods. So this was all driven by the trail scammers and the same Dover NIMBY's who wanted service gone way back when it was still running 4 decades ago. The precedent set by this is awful. The NIMBY's ran totally roughshod over the ROW from Day 1, and couldn't have been any more obvious about broadcasting their intent to salt over the ROW. And now they're stabbing their own trail lobby in the back NIMBY'ing that. The ease with which they got away with it and were enabled by their local Legislators is scary, and emboldens every other spoiled-brat little 'burb in the state that much further. The wag-the-dog effect is out of control.
Unfortunately it now makes no sense to run a branch to Millis off Walpole Jct. via the Framingham Secondary to try to give them some token rail service. That leg of the wye misses the Walpole platform altogether, and getting to Medfield Jct. then Millis requires a few miles of very inefficient backtracking on track that lacks the geometry to ever go that fast (unlike the much more direct and grade crossing-few lower Framingham Sec. to Foxboro). There's an MPO study about better bus connections from Medway and Millis to Norfolk station via Route 115. That's probably the only viable way to improve their transit access. For Medfield a bus down Route 27 to Walpole is their best option, since the long-term passenger potential and schedule practicality of running a Franklin-Worcester connecting branch on the upper Framingham Sec. is negligible at best.
And, really, it no longer makes sense to hold the Needham Line open for future restoration now. A Millis branch wouldn't have solved the NEC congestion that's leaving the Needham Line odd man out on any meaningful service increases. A far, far greater audience gets far, far better served doing the Orange + Green extensions they were supposed to have done decades ago.