Europe generally has a roadworthy like in NSW after 5 years and then every 2 or 3 years depending on the country. They check lights, brakes, steering, suspension, anything safety related basically and then the vehicle also has to pass an emissions test. On top of that i.e. in Germany the road tax is linked to emissions and unless you are in the top 2 bands you will pay about 5x rego. Can be occasionally a problem with older petrol cars. Once the car reaches a certain age it actually does not have to pay road tax anymore (30 years or so) as it counts as an antique. Makes it very annoying to drive cars older than 20 years old as you pay through the nose to keep them on the road.
My parents recently fitted their Diesel with some new particulate filter/exhaust processor. And they only have a 'small' 2L diesel. If you plan to keep the car for more than a few years longer it is worth it because you pay less tax.
QLD has no inspection, you can get a roadworthy certficiate which lasts 3months/1000km but it is only for selling the vehicle really I think. I had a look at mine and it looked rather "light". The only useful thing they check is brake alignment and wear imho.
I'd be a big fan of emission tests as I cycle a lot and it is quite frankly sometimes unbareable if a Diesel V8 SUV overtakes you on a 8% incline and a cloud of black smokes surrounds you and you cannot breathe. Im actually somewhat convinced that this is a deliberate choice by the manufacturer as exhaust filters reduce horsepower and since exhausts dont matter in Aus there is no incentive to filter the exhausts.