No, it hasn't been. Read this article
They let the word out that it had been a hoax, but maybe you're right, except the story may have been garbled and 911 may have been called as they fell to their deaths in the collapsing debris, but by the time the operator came on there was no sound of life and cell batteries went dead in a couple hours at most, ending any search possibility of locating them alive.
The denial may have been carefully parced, saying no one talked with operators on the phone after the collapse. I don't believe the reporters asked the right question, was there a 911 call or calls and was there an open receiver at the other end.
When they let us hear the sound after the collapse there was the eerie sound of hundreds of crickets---the fireman locator signal on all those dead firemen going off at once.