Below are links to the presentation from a Urban Ring meeting earlier this month. It shows plans for a bus stop at the intersection of Stadium Way and Western Ave and one at the intersection of North Harvard and Cambridge Street. There is also a bus stop and commuter rail stop behind Malvern St near the BU campus.
This route through North Allston clearly favors the eastern side of the neighborhood and Harvard's future campus. A route slightly to the west (North Harvard St to Franklin St to a commuter rail stop near the Sports Depot - drawn in red) or further to the west (Everett St to Cambridge St) would more equally serve North Allston and North Brighton and put the commuter rail station within walking distance of a larger population that now has no good mass transit access to downtown. It seems rather redundant to put a commuter rail stop so close to the existing Packards Corner stop on the B branch of the Green Line.
Complete presentation (7MB file). Slides most specifically referring to Allston