I did the exam in 2008, but I do know that the administration does not give you back marks. So you will never know the "average scores" for each section. And to be honest, it doesn't make a difference anyway; if you're well prepared, statistics do not mean anything.
Each year, over 1500 boys sit the exam. The scores required to get in are different for every school. I went to Rowville Secondary, and I only needed one superior, two above averages and three high averages to get into the school. I have a friend who also had no superiors and got in. However, this is only the case for really bad schools. If you went to a school like Glen Waverley or Brentwood, people needed at least three or four superiors to get into the school from what I've been told.
My advice? Do your best, focus on exam technique, and don't think about the chances of getting in or not.