I had a similar experience nearly cleaning up a para glider between Tyabb and Tooraddin about 6 months back. This clown was in CTA as well and I could see the blokes face. We were on descent into MB and reported the matter to the services but nothing every came out. We were probably only 20 meters away from each other.
I do believe I have met the bloke that we nearly collided with and said that he regularly travels along this route with no radio.
What a muppet