The T starts six weekends of shutdowns on the Orange Line between Sullivan Square and Tufts Medical Center starting at 8:45 tonight. There will be bus service between Haymarket and Sullivan Square; people heading to State, Downtown Crossing and Chinatown will have to transfer to the Green Line.
That should be especially fun for those hypothetical riders trying to get from Forest Hills to, say, Assembly Square, but the T says it'll all be worth it in the end after they've finished making Downtown Crossing, Haymarket, State and Chinatown shiny and newer, with new signs and everything. The work also includes replacing a total of about half a mile of track.
The addition of these 6 weekend shutdowns allows the MBTA to complete work on the Orange Line level of these stations almost a year earlier than previously planned.