The MBTA puts out an RSS feed that an enterprising developer (or frustrated MBTA commuter) started scraping and turning into tweets.
This app scrapes the MBTA's readtime feed feed, and will tweet out the short descriptions, with the hashtag #mbta.
FredHQ, the creator of @mbta_alerts, almost suspended the account due to a number of obstacles, but Code for Boston offered to take it over. Fred provided thorough documentation of his processes, which led to the development of this app.
Then for the 2014 national day of civic hacking Calvin Metcalf creatted a whole slew of single line accounts on top of the origional one.
MBTA Alerts uses: