1. I've read about NEW_AUCTION_UPDATE and it appears to be exactly what I need to track, but I can never get this event to fire. All my other AH events fire perfectly.

    Is there a trick with this one? has it been deprecated?

    There is no trick. If you open the auction house, go to the 'auction' tab and then place an item in the create new auction window.. the event fires. I've just confirmed this.