So I’ve seen MBTA Commuter Rail through the center of town, but what line is it? Also the Medfield Junction, what are it’s uses nowadays?
The line is currently known as CSX Framingham Secondary (although the track is owned by MassDOT with CSX having exclusive freight rights). I think the line sees a pair of road freights daily that may operate at night. The line was created as the Mansfield and Framingham RR in 1870 and has been through a number of owners over the past 140+ years.
https://en.wikipedia.org/wiki/Mansfield ... m_Railroad
Not sure why you saw an MBTA train but I'm guessing it was a track inspection movement - was Amtrak's "Corridor Clipper" geometry test car in the consist?