by SCB2525
The MFL does not have the capacity to allow an extension appreciably far up the Boulevard, though the plan always was to extend it TO the Boulevard to meet a BSL extension. The BSL was designed to a much higher standard with 4 tracks specifically to accommodate (several) extensions. You would only need to tunnel from the end of the ramps north of Erie to some portal of a location as yet determined (I don't know if planning ever got that far).