PMT Project List - This is a huge list of possible transit improvements in the Boston area. It includes some relative to our area, like "Add an outer Urban-Ring from Harvard Sq. to Dudley via Allston and Brookline (Route 66 routing)", adding a commuter rail stop, and extending the Silver Line.
Here on the ne.transportation newsgroup is a long discussion about the feasibility and importance of the possibilities.
"what I need is transportation from Allston to Kendall Square and that doesn't exist... at least not by rail."
"I keep wishing the Framingham/Worcester line still made its ancient stops near its east end, including at the former Allston Station, now the Sports Depot bar. (I think other ancient stops include Market Street, Brighton, where the former station is now the Stockade restaurant; one near where North Beacon Street crosses the river; and Newton Corner.)
At Newton Corner, the trouble is that a new service has to comply with ADA, and at that station it's difficult. At Allston, I suppose CSX wouldn't be too happy about a passenger stop right at the edge of its freight yard."