A few things:
The walkways through the windows are still used, and still glass-floored. But they're not open to the public, and in recent years (decades?), their access doors have been equipped with automatic locks.
The concourse floor is not 81 feet below street level, or even 30. More like 15. The concourse itself is 150 feet high, so I have no idea where the figure "81" could have come from.
The "shoot to kill" story in the Journal News article is true, but misrepresented. Most critical facilities during the war--stations, post offices, etc.--were guarded by troops with that order, but the order was to be carried out
only if the trooper was challenged (ie, "oops, I took a wrong turn" would get you detained, not shot). Furthermore, "shoot to kill" is not a summary death sentence. It simply means fire without warning, and continue firing until the challenger is down. Preferrably, the person will live, so he can be interrogated later. However, if the person dies, the guard is not held accountable. (Those were the sentry instructions I got in the Navy. Any grunts here who were told differently, feel free to pipe in.)
The famous steam tunnels--AKA Burma Road--once frequented by "industrial archeologists" (including myself, long ago) are kept under tight lock-and-key these days. Attempts to explore them
will result in lengthy detainment. Needless to say, they were never open to the public, and were only sporadically inhabited by homeless folk. The equally-frequented baggage tunnels, however, are now very much open to the public in the form of the new Northwest Passage.
Anyone whose gone googly-eyed over reports of mysterious "multiple levels," as depicted in Jennifer Toth's book,
The Mole People, had best read
this.