From a Meredith Slesinger, MA DOT Rail & Transit Administrator, 5/16/23 East-West Passenger Rail presentation including South Station expansion and adding a 3rd main CP-11 to CP-21 is this slide about first-step Worcester-Springfield and G&U interchange improvements supporting 2 additional Inland Route passenger train pairs. It's a $135m project for which MA DOT has applied to 2 grants anticipated to be announced Aug-Sept and Nov-Dec.
Noteworthy is extension of double main track CP-48 out ~2.4 miles to around Webster Jct. QB 50.7 likely indicating continuing use of Worcester as a hub to mix & match traffic using main track west of CP-45 and instead of possibly adding track along the Worcester Main Line south of Barbers as has been pondered over on the Pan Am threads. Additionally, double main track will be re-installed from CP-83 to CP-92.
The slide also shows construction of passing sidings west of Rochdale ~QB 54 to CP-64 and CP-79 to CP-83. The former might indicate within that mileage, amongst what's being planned, a signaled siding 3rd track around the E.Brookfield/S.Spencer auto site while the latter a signaled siding in addition to 2 main tracks west from CP-79 accommodating a planned Palmer passenger station.