you're historically right about this, but wrong on a bunch of other levels. there is a few million square feet of real server colo in 111 8th ave, and at least an order of magnitude more than that combined across the other spaces mentioned.
The reason they locate there (as with in London) if to reduce the latency for financial trading programs. It may not sound like a lot, but when you have an automatic trading application processing billions of trades a year it can make a huge difference to receive the information a little earlier, and place your orders that little bit quicker.
As a side note, Internap's LGA11 datecentre facility on 75 Broad Street is currently being evacuated, and most of the fuel reserves are submerged below water...
