NBA 3/4 Time specials

Hey, Australian Bookmakers have alot of 'if your team leads at 3 quarter time and loses, we'll give you a bonus bet up to $100' and at the moment they are running this special for the NBA. To work out the profitability of this special, I want to work out: given a team loses, what percentage of the time were they leading at 3QT. Could anyone point me in the direction to find this information out?