From
http://www.mbta.com/winter/ :
Limited service will be restored effective 2pm, Sunday, February 10, 2013 on the MBTA's Red, Orange, Blue between Orient Heights and Government Center, and Green Line between Kenmore and Lechmere. Service will run approximately every 20 minutes on each line.
Limited service will be restored effective 2pm, Sunday, February 10, 2013 on routes 1, 23, 28, 39, and Silver Line Washington Street Only. Service will operate approximately every 30 minutes on each route.
No
other bus routes or commuter rail will run today.
ETA 5:45 pm: The MBTA web site now shows many more bus routes running today, including the 77 on Mass. Ave. and the 89 on Broadway. I don't see any other Somerville bus routes listed, unfortunately.