In the most recent FMCB meeting PDF dump, there was an item called "Rail Vision".
http://www.mbta.com/uploadedfiles/About_the_T/Board_Meetings/I.%20%20Rail%20Vision.pdf
They are doing a 2-2.5 year, $2m study to model different service scenarios. It pays lip service to looking at RER, S-Bahn...