North Station land doesn't need to be freed up. Jerry Jacobs has air rights over the platforms to do as he pleases whenever he's ready for an back-side encore to Hub on Causeway. Ask him about that one, because he's the oracle there.
"Central Station" only exists on the CA/T alignment as a deep cavern underneath Aquarium for Blue Line transfers. It's not a drop-in for NS at all because no Green or Orange access, and no surface access. That's why it's strictly tertiary importance to NS Under and SS Under.
On the Congress St. alignment there's an offset station at Haymarket that hits Green/Orange but omits NS Surface because the cavern is too far away from there.
One thing to remember is that none of the cavern stations are geographically 1:1 with the locations of the surface stations, so all this kvetching about "North Station is in the middle of nowhere" are missing the point. We're getting hung up on 2D map positions where not only is this very much 3D at near-100 ft. below ground but the platform positionings on renders say nothing about where the egresses from those platforms are going to go. The CA/T alignment's NS Under gets within 1 block of Haymarket on its back-end footprint. That's close enough that it
will have a secondary egress into the Haymarket rapid transit headhouse. The Congress & CA/T builds are functionally zero-difference at providing full access to more-centralized Haymarket. They're both deep caverns and a relative P.I.T.A. on escalator transit to the surface exits. So it's not much functional advantage that the Congress alignment is more physically centered under Haymarket while the CA/T alignment straddles NS + Haymarket with a slight lean towards NS. They're both going to take about the same amount of effort to get upstairs to rapid transit or the surface exit.
The CA/T alignment's already got the major advantage in that it can be 2 or 4 tracks on the same footprint vs. Congress which is 2 max and requires the CA/T alignment to be built in (pointless) duplicate to get Tracks 3 & 4. The fact that the CA/T alignment's NS Under is going to have combo-egress Haymarket + NS rapid-transit/surface-exit accessibility as the access 'superset' sort of settles what's left of that debate. You don't have to debate the particulars of 2D map-landmark NS being too off-center from the action and 2D map-landmark Haymarket being closer. It's irrelevant. The dang build will have exits into both by default, and if there are any access demerits whatsoever it's depth not linear placement that's going to be the limiter anyone notices. Nobody's pretending the escalator trip is going to be all that brisk from a cavern so deep, but there's zero solves for that given the engineering paths left to choose from and that'll get noticed more at SS Under to begin with since that's the busier station.
What's central vs. not-central on surface placemarking is an irrelevant argument to get distracted by. Actual egresses to what's most-central are covered by any permutation of the base build Alts.
They do, but it's still a shitty idea for traffic management because reversing slots on-platform in the tunnel is utterly wretched waste of capacity. And see prior post about the Western Route/Reading Line's gimpiness being a problem for chaining, so even the assumption of getting rid of the surface terminal for the sake of turning stuff at Westwood or Dedham Corporate starts to eat into that Japanese schedule-adherence 'golden rule'-age that makes the whole blended system cook. The arguments for doing away with NS Surface are all pretty weak, and a bit too precious at integrity-of-concept overruling practicality.
Today's north-vs.-south traffic comparison isn't a relevant comparison because north is getting the same re-fitting to RUR :30 / Urban Rail :15 bi-di all-day frequencies as south. So the gap is going to close because the present starting slate of frequencies is so much weaker than the south schedule-by-schedule, and will be upscaled to standardization. The north-south differentiator is going to strict-arithmetic
number of schedules run out of SS, and no longer number + north being the born weakling. There's going to be a metric shitload more slots infilling NS right from RUR Phase IA on, such that by the time you get to NSRL those traffic levels are going to be so much higher than today that "integrity-of-concept" zero-out starts to look awfully impossible. The RUR upscaling is an order-of-magnitude change in itself. And by virtue of that, giving RUR + Urban Rail 20 years to cook before any tunnel opens is going to move the needle gravitationally on that whole "NS isn't central enough" debate. The frequency growth's going to make it way more central than it is today, such that this already false-argument for NSRL is going to look real muddy. Doesn't matter in the real world because building the most buildable alignment gives you the dual NS & Haymarket egresses to begin with...but for "centrality" purposes the NS egress is going to have grown quite a lot beforehand by all the add'l RUR action.
And...as mentioned first off...there's zero real-estate coattails to eliminating NS because Jerry J.'s already land-parking on the air rights for the backside and will have made his move way before NSRL comes out of design and is deemed shovel-ready. Given all else that's ops-easier and all else that the CA/T alignment NSRL covers its ass with egress options-wise, might as well keep the train station if there's already going to be another big-ass tower sitting on top of it as an additional driver.
Judges...how'd I do? Too consise? Not vitriolic enough?
There's something very blinkered about over-projecting to such degree that there's some sort of "game" being played here. Maybe back off the leading pretenses a bit and you'll enjoy the discussion more, dude.