^Very cool.
I see there are always 1-2 security guards down in the Comcast Center food court where the tunnel begins, and the area is roped off-- I'm so tempted to try to sneak back there and check it out.
The spine still has a little ways to go, more than 6-7 floors-- but it is making good process.
As far as Comcast 3, at the corner of 19th and Arch (the parking lot) - the Byers School next door has been building some odd 2-story addition to the back of the building. So it does not seem like they are going anywhere.