The acting in the video is horrible or, "harrable" as Howard Stern would say.
I would beleive that there are complex tunnels underground. But I think everything else is stated in the video is a hoax.
There are high speed trains in these tunnels. They use mag lev tech, and suck all the air out of the tunnels so that there is no air resistance. The trains can go like 3000+ mph. The system was designed to haul sensitive cargo from place to place including nukes, and whatever else they didn't want the Russians to see.
The facility was expanded to as many as twelve levels and several hundred workers. Some reports have the facility extending under the town of Montauk itself and interconnected with vast maglev train tunnel networks to other "Deep Underground Military Bases", also known as "D1 Bases".