Liquid Nitrogen Tank What Are The Liquid Nitrogen Tanks On The Streets Of NYC For?

What are the liquid nitrogen tanks on the streets of NYC for? - liquid nitrogen tank

There are many standing on the sidewalk, especially in the inner city, all with ice and Ruber pipes snaking underground fall somewhere. I have a picture here: ... http://www.flickr.com/photos/emilywhetst
My guess is that the cryogenic cooling system to transfer quantum encrypted communication channels, the sensitive data among banks, but surely there must be a simpler explanation.