there used to be an RPL for people holding glider Silver and Gold C certifcation.
Indeed there was, well at least it applied back in 1982 when I started my training.
However I do not recall actually seeing anything in the ANOs or ANRs. (as they were then) My Instructor at the time just told me to take my Gliding Log Book into 'Aviation House' in Adelaide and speak to one of the Staff there.
I did so and was granted (from memory) 10 hours off the UPPL. Have no idea now if it still applies.