No, but it would have killed a lot of people and made it impossible to use the tunnels for some time. Plus the psychological blow to New Yorkers would have been enormous. I lived there and moved away just before 9/11, but I have friends who lived through it, are still there - and worry every time they go down into the subway. Imagine how New Yorkers would feel if these guys had pulled off their massacre.
My mom's Godson is still in therapy and he escaped running over bodies. His mother also escaped and still cries to my mom on the phone her story is "it was the end of the world as they sat in boats in the harbor and F16's flew over" This has not passed for NYers.