Wu can't do anything, the T control board answers to the governor (which is a whole issue of its own). Baker created the control board to manage the T’s finances, management, and operations to ultimately "fix" the T. This idealism was thrown out of the window in 2021 when he appointed the current board, so we're left with a powerful board that does jack. Healey would need to directly intervene and appoint a new board or even create some form of new governance, which she seems totally uninterested in doing as of now.