With DD3, my dating scan was out by 12 days according to my LMP dates. For me though, it wasn't really a problem as I never reach 40 weeks anyway.
If your dates are only out by 4 days, I wouldn't worry too much. If you do transfer from Tassie to Qld though, wouldn't your Qld OB request your file from your Tassie OB? Then he/she will know your dating scan dates??