I just finished Deus Ex.

[WarLocke]

The hatch Paul mentions, if memory serves, can only be opened from a computer room in the basement of the building. Unless I'm confused and he meant the one by/under the boxes? The layout of the building changes between the times that you visit it. If Paul mentioned it being hidden under boxes, you'll have to hack it open from a terminal on the second floor (I think...) and the hatch itself is inside at ground level, in the kind of half-room off to the side with all the shipping boxes.

After you deal with the little party at Paul's apartment, he tells you how to get to Battery Park. Oh and also, don't worry if you get "killed" in the fracas. It's the one point in the game (that I know of) that "dying" doesn't end the game.