The MBTA has an internal shuttle route for the Medford Branch Shuttle
The map can be accessed here.
https://www.mbta.com/schedules/Shuttle-EastSomervilleMedford
NOTE: The URL link will expire into a 404 page after the MBTA refreshes the internal GTFS underlying schedule data. This usually happens the day after or two, up to a week, of the shuttle buses running when the MBTA deletes the shuttle routes from their list of routes.
Magoun Sq. stop will be located a half mile away from the train station, use the Route 89 stop to access the shuttle buses. Shuttle buses will not serve the Magoun station's location directly, as they must use Route 89's bus route on Broadway due to hilly terrain.
Buses will loop at Medford at Boston Ave. Outbound buses will use Boston Ave. Inbound buses will use Powder House Circle.
The bus stop in Medford will be located ~600 feet southeast of the train station. The stop will be located at College Ave @ Boston Ave (ID: 2379) at the southwest corner of the intersection.
Buses will loop in Joy St. in East Somerville. Outbound riders toward Medford will ride around the loop back to reach McGrath Hwy.
Shuttle buses will omit Cross St. and instead deviate to Medford St. as a diversion, unlike outbound Route 80 buses.
Note. Eastbound service travels towards Medford, Westbound service travels toward Lechmere. Directions are opposite what the MBTA website displays.