Another consideration for FDNY is the cost. I'm sure they won't be cheap, especially when they're first introduced and with the budget crisis I'm sure a mass change of cylinders wouldn't come to the top of the list. You might see a few for the rescues or something like that for testing.
One interesting point to consider is they probably won't have to be hydro tested. There is a certain volume below which ASME doesn't require testing and I'm sure these are well below that volume. That would be a potential cost savings. I do wonder about the long-term durability of this system, especially the flexible connections between the cylinders.