I guess I'll bring this up again: The Silver Line extension is a good start, but nowhere near sufficient for moving game-day-sized crowds. The stadium will have 25,000 people leaving at the same time. Really generously, the Silver Line can move 2,000 riders per hour at current normal peak operation (100 riders per bus X 10 buses per hour X 2 directions). In three hours, that couldn't clear a quarter of the stadium.
The MBTA can absolutely do a lot to move more people on game days. For some wild guesses what the T will have to figure out by March, consider: What will it take to run a bus every minute? Every 45 seconds? How can they run almost an order of magnitude more buses than they do for normal rush hour? Where will those buses come from? Will they have to buy more? Where will the extra bus drivers come from? Is there space for those buses at Sullivan? What physical infrastructure is needed at the stadium bus stops? How much space is needed for thousands of people to queue for buses while letting others get by on the sidewalk? Which cities and which city departments will be in charge of crowd control, traffic control, and maybe closing streets? Who does the T need to coordinate with? How does this affect other planned street redesigns? Will the Orange Line need to run more frequently on game nights? What about frequencies on all the other bus routes at Sullivan? Or commuter rail? Should there be special game-day buses express to other transportation hubs like North or South Station? What percent of the stadium could the T actually transport in a realistic timeframe? How much will all this cost?
I don't want to give the impression these things should be overwhelming or impossible. But the Silver Line really isn't enough, the planning isn't trivial, and the implementation will cost money. The T needs a rough estimate of that cost by March, and then various stakeholders will spend the rest of the year fighting over who pays.