MBTA Commuter Rail recently tweeted out two photos of the rail destressing project. More details about the project here. This also explains the station closure - you really don't want to be near chopsaws and open flames while waiting for your train.
As of late October 2017, the author is an MBTA employee. Blog posts prior to that time were created when I was NOT affiliated with the MBTA nor Keolis and therefore were my own opinion. Blog posts after October 2017 are my own personal statements and do not represent any official position or opinion of the MBTA and should not be construed as having been endorsed by the MBTA.