I get confused by the talk of Australia being a dumping ground for high emissions vehicles.
Part of the reason we lost our automotive manufactures was we weren't a big enough market for vehicles that are only sold in Australia. Much more efficient to build 1,000,000 vehicles in Thailand and send 10,000 of to Australia than it is to have a "small" manufacturer build 10,000 in Australia.
However the media/government tells us it is more profitable for a manufacturer to build 990,000 high efficiency vehicles on one production line, and build the odd 10,000 low efficiency vehicles on a low scale line instead of just having one production line.
So to rectify the issue we have impose efficiency standards on manufactures to force them to take the "high profit margin", small scale production line vehicles out of the market and instead give us the "low profit margin", high volume production line models.
Ironically the heavy vehicle industry has to be minimum Euro 4, but you struggle to buy anything less than Euro 5 or 6 (as far as European trucks are concerned). We just get what ever is coming down the production line.
I suspect in reality the light vehicle market is the same.