The fact is if you apply for a 309 (Ofshore Partner Visa) and then get a Visitor Visa to wait some of the process time in Australia - you are eligible for Medicare while in Australia on that valid Visitor Visa.
* A Permanent Residence visa application must have been made (Both 820 &309 include the PR application) - you then need to be in Australia on a "valid" visa.
The exception is the Parent Visa and Protection Visa.