Real-time information about shuttles is only available for buses operated by the MBTA. Shuttles operated by third-party carriers will not appear on the map. Bus icons indicate which rail line the shuttle replaces, however this information may not always be correct, and not all shuttle buses may be tracked. Buses may be tracked on the map as they travel between the shuttle route and garage, so appearance on this map may not always indicate that the vehicle is accepting passengers. Route shapes are not available for emergency (unplanned) shuttles.
Learn more about the data
from the MBTA. Find this project
on GitHub.