The report comes from Joystick, although GoNintendo seem to have a different opinion, backed up by an official flyer sent in by one of their readers (which you can see in the upper left corner). According to the writing on the flyer, “Nintendo Wi-Fi mode means head-to-head and co-op multiplayer mayhem”. Which is quite the opposite of what Joystick reports, and something we would really expect to receive from the handheld version.
So the flyer seems to be the more solid proof, but we still have to wait for an official statement from Rockstar regarding how exactly we’ll be able to play GTA: Chinatown Wars in multiplayer. Until then, all we can do is wait with patience and remember that another highly anticipated game for the Nintendo Wii this time will not feature LAN multiplayer: The Conduit.