to run the E line, they seem to have the darndest trouble. The latest issue, as per this T alert:
Green Line E branch service suspended between Prudential and Heath Street in both directions due to demonstrators blocking the tracks. Use Route 39 for service between Prudential and Heath Street.
As a point of comparison, MassDOT didn't detour traffic off of I-93 at exits when the Somerville 17 blocked it. They let the police move the protesters off the highway instead. Too bad the MBTA apparently doesn't have the common sense to do similar here.