When we leased a flat and got credit cards in NZ they only checked our credit with a NZ credit bureau, our U.S. credit history was never checked and counted for nothing.
I think that the NZ Drivers License number is used to identify credit history similar to the way SS# is used in the U.S.
In my experience the Banks in NZ prefer to give credit to customers that bank with them, when we applied for credit cards we were quickly approved by the banks where we had accounts and denied by the banks where we had no accounts.