I found this presentation linked from an invitation to an upcoming public meeting regarding the I-90 Allston interchange. The meeting is June 17th at 6:30 PM and the invitation is available here.
West Station is part of the I-90 Allston Interchange project. More information about that project is available at the links below:
Mass DOT page about project
Documents available from Mass DOT
Boston Globe article about West Station
December 2014 presentation