The fate of the MBTA's green line extension is scheduled to be decided today.
Building a new spur of the Green Line through Somerville and out to Medford has been a goal of the state since the Big Dig. But estimates putting it about a billion dollars over budget forced MBTA management to reevaluate whether the project is worth it. 
If the MBTA Control Board cancels the project, the state will walk away from $1 billion in federal funds..
Plans have been scaled down already, and Somerville and Cambridge are willing to chip in up to $75 million dollars - but that may not be enough to save the almost three-billion dollar project when the rest of the T is in such bad financial shape.