Originally Posted by IMOA

What probably saves you is that the debts are to the state government, not the australian government, and they haven't got things linked up. What may be important though is that if you've got unpaid fines they will "cancel" your licence for that state. I'm not sure how well set up the databases are but at some point you might end up with a fairly firm conversation on the side of the road which ends with you doing a lot of walking. Worst result would be if you have an accident and find that any insurance you think you have is void.

Not trying to do a lecture (if you saw the state of my driving record in aus you'd understand why I'm not) but just a reminder that visas are issued by the federal government and speeding fines are issued by state governments so not paying speeding fines is highly unlikely to cause an issue getting into the country but could cause some huge ones once you're here.