The BG96 has been approved in Australia for RCM (a mandatory Regulatory Requirement) and Carrier Certified by Telstra for CAT.M1 since February 2018. The BG96 has also been certified for NB1 on Telstra’s Network, and also on Spark New Zealand for their CAT.M1 network.
The only Australia carrier at the moment offering certification is Telstra. This is not a mandate and yes, you can buy ordinary pre-paid Telstra SIMs at the supermarket and usually connect to their network without issues. This is only for testing and these ordinary SIMs are not guaranteed to always connect to CAT.M1 or NB1. For long term use, their M2M SIMs should be used, usually administered by their Jasper web portal. Telstra certification tests are quite rigorous and certification is considered more of a quality check with more of commercial benefit than a regulatory requirement. Sometime, even Vodafone or Optus customers request Telstra Certified products because of the strict testing that goes with such certification assuring Quality of Service.