You would if your concern were really terrorists instead of laborers.
BTW, remember the Tennessee Driver license scandal? One of the people that woman they burned alive issued phony licenses to had a contractor's work permit to 'fix' the sprinkler system at the base of the WTC dated a few days before 9/11.
The WTC didn't contract out such work.
If you were paying attention, you might have noticed the smoke was jet black, not the paler steam diluted color that you get when water actually makes it to a fire.
Interesting coincidence isn't it? A common laborer shows up a day or two before a major terrorist event, and the emergency equipment malfunctions right on cue?