I don't know the answer , but what other countries do not allow Private plates?
I believe Germany doesn't allow them, although you can select the letters on it to be your initials.
I've also heard that countries like Australia and the US aren't as tight on the combination of letters and numbers as in the UK, so in theory it can say anything! That might depend on which state you're in though.
I keep looking for my perfect one, but my initials are JAG and therefore the limited few that are still available are a fortune