We do have road registered versions of the cr and rm except it's called a crm and rmx or rmz depending on year. I have also seen a yz 125 registered in Brisbane. I don't know how they went about it, but it was road legal.
That Brenda Raymond that was lurking around, asking mainly stupid questions did ask about registering an rs250 in Australia. I reckon it's possible to do over here if you are willing to jump through a lot of hoops and pay the right people. The real question is would it be worth it.
Andy
Bandit7