Pataki may not know. But a "veteran captain," Ben Tillman, was just on MSNBC and said that fuel can be dumped at any time, and that fuel spewing out of the plane could have been a compromised fuel line which could result from a catastrophic engine failure, or could, indeed, have been the pilot dumping fuel.
Sure, you can press the button at any time, but pilots tend to follow procedure, and there wasn't time for a fuel dump procedure. We'll know when they check the cockpit switches and dump valves.
/john