When I was in Hong Kong in 2007, there was pin trading at the Disney Store at the airport. I unfortunately did not have the chance to go the HKDL, but I would imagine that if trading was happening at Disney Stores, it was also happening in the park. Plus, they do sell pins at the resort, so it seems unlikely that they wouldn't trade.
But I can't say for absolute certain. I would recommend seeing what people are saying on the HKDL board. Or maybe try some Google-Fu and see what the rest of the net has to say?