I know that the AT+T unlocked stuff can BUT (and this is from HTC experience)... Dont let it try to do an update with a telstra sim in it over the network, set the updates to manual only, remove the sim and then run the check for update + update over a wifi network if it still wants to update reboot and put the sim back...
as a side thought you might be able to get the 64 on a telstra plan from somewhere like JBhifi...

