Last year, I rode the Mass Bay RRE's Berkshire County Rambler. It was a truly great excursion, running from Lenox (BSRM HQ) north to Pittsfield, then south to Great Barrington, and back, utilizing BSRM and HRRC motive power, plus cars from the BSRM. There was a lot of great cooperation on this trip, as it went far beyond BSRM's regular jaunts. Last summer, the HRRC and BSRM again teamed up for excursions out of the Canaan (CT) Union Station. I was hoping to get on the one from Canaan to Great Barrington to complete my "Berkshire Line" mileage from Danbury to Pittsfield, but opted out, as it would've put me back home in VT way too late. I'm kicking myself now that I passed on that trip.
Hopefully this is not the end for BSRM. They had a really great operation going, a descent amount of equipment (rolling stock and locomotives), and descent patronage, especially during the holidays.