"Please feel free to contact your local firearms registry, police ministry or member of the legislative assembly using the letters and information provided on the NSW page to try and change this."
As Trent said, the person who created and maintains that page is a member here. He contacted the NSW police ministry and worked hard to obtain a legal avenue for ownership here. If other people want to do it for their respective states/territories, then you're welcome to follow his example and do likewise.
Australian Customs has learnt how to detect Megatrons in robot mode since 2007. Before then I used to have them shipped in robot mode. Since then, I've acquired a permit. :)
It's easy for you because Gunformers are perfectly legal without restriction in WA. But as Customs is a Federal and not State body, they may still confiscate the toy and issue you with a notice. If that happens, you simply need to contact Customs and inform them that you live in a state where the toy is not illegal or prohibited, then organise a time to collect it.
Correct me if I'm wrong, but I believe that these toys are legal in Victoria, however they're prohibited like in NSW, meaning that you'll need to conform to safe storage requirements and acquire a permit as we do here.