The pre-1997 North Station Orange Line station was very similar to Tufts Medical Center station. They were built at about the same time, presumably designed by the same concern. The original North Station didn't have the south end exits and fare lobby that Tufts does, that was added to North Station during the superstation construction. When they constructed the Green Line addition, I recall they dug out and constructed the tunnels and track areas, and then cut out the original outer wall dividing the two sides. I passed through there on a fairly regular basis back then and remember one day the wall was there, and the next time I went through (probably not the next day, but maybe the next week), it was gone. The tunnel dead ended on the north end of the platform where the portal is now, that was punched out later, after the tunnel under Causeway St was built to connect it to the already-constructed tunnel under the new Boston Garden. If I recall correctly, for a short stretch of time, some branches terminated at North Station (probably the ones that terminated at the surface stop) and turned at the platform, or, after it opened, used the yard under the Garden to turn, while others went up the incline to the El to Science Park and on to Lechmere. And then in 2004, when the Lechmere Viaduct was connected to the tunnel under the Garden, the el and incline were closed and eventually removed.
