Certainly there are basements. Possibly they are still somewhat intact. Certainly people below were evacuated, but could there be people holed there. Plus automobiles that are drivable. would the force of the collapse destroy the basements?
From street level you would have gone down a story to a shopping concourse that underlay the whole complex. Off the concourse were NYC subways and maybe 10 stories down was the PATH terminal - the PATH is a train that goes under the hudson to NJ. I don’t know the garage/service basement complex too well.
The towers must have crashed in and filled the deepest recesses of the basement (not surprisingly) otherwise I would have expected to see survivors escape out the train tunnels and exit to the street or even all the way out to NJ, but as far as I know this hasn’t happened.
People have been found alive in pockets, and they still have an unimaginable amount of digging to do, so time will tell.