Fixed the video link.
I'm not really sure why they chose to scale back the central chiller plant in the new complex. They did rebuild one that utilized the Hudson river, but it only cools the underground spaces, such as the 9/11 Museum, PATH, and Westfield mall. I'd imagine they chose to have the buildings handle their own cooling needs for a few reasons, namely underground space is limited and the designs / plans for the new towers was not finalized, and therefore it would have been difficult to design the plant which was needed sooner for the museum. Also, the river gets pretty warm in the summer, so mechanical cooling is required. I think in the end, they chose to downside the chiller plant and rely more heavily on "energy efficient" mechanical cooling.
Here's some information on the new plant.
(pdf). Here's another.
I found more info on the original chiller plant for you. The original plant consisted of 7, 7000 ton centrifuges, and 2, 2500 ton units. After the 1993 bombing, a second plant was added which houses 5, 2500 ton units for a total capacity of 64,000 tons. The new plant only has a capacity of 20,000 tons. Check pages 8-13