I think the problem is, that there's no berth that is permanently vacant that is big enough to park it. There's really only Burnie, Devonport or Hobart that has port facilities big enough, Devonport will still have the current ferries coming in and the regular freight ships, and berth 3 is still under construction, if parked at either Burnie or Hobart it will block the docks use for freight services.
It all started when the state government dropped the initial preferred contractor of Devonport's Berth 3, because of a cost increased, but this action not only blew the timeline out a couple of years to secure another contractor but also increased the cost a whole lot more than the initial cost increase.
The handling of the new ships was no better. First off, the German company went bust (that was out of the governments control), then a Danish company was chosen but before they could start, the state government decided to halt the construction to see if an Australian builder could do the work and of course we don't have any experienced roll on roll off ship builders, so surprise surprise, they had to go back to the Danish company to say that they would like to now go back with them and of course they said, well you have lost you spot in the queue, and it will be millions more expensive now.