The Squarespace blog is the company's official site for product news, funding announcements, developer platform updates and its SSL rollout.
HN links it in outage and hosting discussions, where a Squarespace employee points to it as a site still served from the Peer1 data center.
Yes, it's still connected to the outside world, and has been continuously thus far. Example of a site still being served from machines at Peer1: http://blog.squarespace.com/
(I am a Squarespace employee)
Squarespace is one of the companies in that data center. See here for their story (and some photos):
http://blog.squarespace.com/
http://status.squarespace.com/