I've just come back from my local EB Games here in Australia. From the information I was given, here's my understanding of how the Ghost Editions are distributed in Australia:
The example from my store: This particular store was allocated 3 Ghost Editions to distribute. The only people eligible to buy this were 18 people that had already preordered in store with a deposit over $50. The store manager will ring each person on that list of 18 in order of purchase and ask if they want to upgrade to the Ghost Edition. If the first 3 decide to upgrade, the other 15 miss out (but will keep their preorder of the standard edition of course).
However, I'm not sure how this relates to platform. They may have gotten 3 PS4 versions, or some mix of different platforms.
I was told that anyone going to preorder the Ghost Edition today (like myself) would be flat out refused. But he would gladly take my money to preorder the Limited Edition.
All I can say is, thank god for my amazing sister in NZ who ordered the Ghost Edition for me today.
Sorry to all those who missed out