I attended a presentation by AEMO last week which confirmed that AEMO uses aggregated PVOutput.org system and generation information (aggregated by postcode) to help them account for the impact this has on their demand forecasting (because residential rooftop is behind the meter, rooftop generation manifests itself as a demand reduction).
It was further explained that AEMO only uses systems which pass their data requirements (I guess completeness, reliability, etc).
I If anyone wants a copy of the presentation happy to share it.