Having only played the PS2 version, I personally can't help you here, but I went looking for you and found this at
www.planettonyhawk.com so credit goes to them for this:-
"The hidden deck is well hidden here, over a quarterpipe located halfway up a building. Grind the right hand telephone wire to reach the quarterpipe, and air straight up to snag the deck. For a real charge, start this off from the electric rail with a manual over the kicker to turn it into one big combo, then revert on the way down and reverse the process all the way back to a huge air off the alley quarterpipe. Or, of course, you could also take it into a longer grind combo around the car wash area to end it with a little revert action... if you're so inclined."
Hope that helps you out...