A helicopter that loses power at altitude can often still land safely due to autorotation. I am no pilot but I've read that the JetRanger is particularly competent in this flight envelope. See http://en.wikipedia.org/wiki/Autorotation and http://en.wikipedia.org/wiki/Height-velocity_diagram for more info.

On the other hand, losing the tail rotor is always Very Bad and quite difficult to survive. It's possible that this is what happened in NYC.