Couple notes about some that aren't like the others. . .
Orient Heights parking sits on a valuable T maintenance parcel, where if the parking needs to go it's because the T is packing more maint facility room in there. Which would most definitely happen if the Blue Line were extended to Lynn, but also if the T needed to house some add'l non-Blue/non-bus misc. 'dirty-work' functions there. That one almost certainly won't--and definitely shouldn't--go for private dev, simply because of how hard it is for the T to find any facility space close to the city. The Quincy bus garage relocation saga is illustrative of how toxic the NIMBY culture is in local politics to transit maint facilities, so they simply must hold onto all property they have that can fulfill that role. I agree that the OH parking is excessive, and probably is fetching too much Logan induced demand. But the only buildings that'll ever be allowed to take away that parking are in-house agency facilities. It's a lot like Watertown garage's parking lot...when the garage closed they simply striped the unused yard space into a parking lot. But Watertown is on the long-range radar for an expansion bus garage to absorb a bunch of Newton/Watertown/Waltham and Allston routes from Charlestown and the downtown garages so the ones nearest the CBD can shape-shift and bank expansion capacity. And, given that battery buses need a much higher spare ratio than fossil-fuel buses for charging downtime, the reanimation of Watertown and subsequent shape-shifting of routes may be needed anyway just to hold down existing service if the move to a large-share BEB fleet. So that asphalt parking strip right on the Charles opposite H2O Sq. is overwhelmingly likely reverting right back to fully-stocked bus yard before this decade is out...so that one doesn't even have time to whip up support for a bunch of SimCity renders before it's off the board. Orient Heights may be a longer-term prospect than Watertown for add'l T uses of the parking space, but you have to treat it almost the same way as property that simply *must* be put to some sort of future-leaning transit ops use for how hard those to otherwise acquire from-scratch.
Some of the Logan overflow lots like the big one on Eastern Ave. in Chelsea on the west side of the river are Massport long-term holds for Deep Port Access activity because of the position on major shipping channel. See the disused ship docks on the river. Until they were demolished in the late-90's, that parcel was extension of the Gulf Oil gas tank farm on the parcel north of Chelsea St. See Historic Aerials; on the '78 view the tanks wrapped all the way around to the current Audi rental car lot on Marginal St. The lots are literally 'parking' the parcels until Massport can find new DPA uses for them. Those pretty much need to be held in perpetuity...no matter how much local & Legislative pols bitch and scream and try to pervert the process...as a later wave of port/shipping/industrial redev after some of the first-wave most attractive Massport parcels are tapped out. Deep ship access in a freshly dredged river, and available freight rail hookup to the Eastern Route if a siding got forked off just east of the Eastern Ave. grade crossing and passed through Gulf Oil property between the tanks. Chances are this one won't be a major redev consideration for at least 20 more years because Massport is busier right now fine-tuning its existing port properties...but with there not being much "seaport" left in the Seaport the 600K sq. ft. on the overflow lot and 400K linear square feet on the Marginal St. strip are their big mid-century leverage for the multimodal access--ship, truck haul road, and rail--that it overs. So if they have to "park" it (figuratively) in the meantime, that's perfectly acceptable future-proofing. At least as parking lots go they serve mission-critical Logan functions, which draws a red line in the sand from too much political pressure to turn it over to someone's pet private SimCity canvas.