I heard that same story somewhere. And the one I heard said they made phone calls celebrating and confirming hits; and they took pictures.
N.J. all gathered on an apartment building's rooftop the morning of the attack and awaited the promised atrocities. That was in Jersey City in the neighborhood that the '93 bomber came from. I can't confirm the truth of the story but have heard it from many. I live in the next town over and have heard of many celebrations on that day in the Arab/Muslim areas.