The story as I see it, so far.
It appears that dealers rather than Ford Australia were the ones to initially accept deposits for Mustangs and it wasn't until the Australian specification was released by Ford Australia that they accepted orders from the dealers (December 2014/January 2015 approximately). Based on some of the comments, it would appear that Ford Australia accepted orders based on timing of orders from the dealers, rather than date of order from the customer when they paid their deposit.
From what I can see on these pages, some customers have been reasonably well informed of the delivery process whilst others have been left in the dark. Pretty unprofessional by Ford Australia and it's dealer network, however, their situation is exacerbated by the fact that Ford America and Ford Australia run different software and hence dealers generally receive a monthly update rather than have access to an international database like many other manufacturers.
Personally, my wife and I ordered an ecoboost Mustang in March 2015 (did place an order initially in November 2014, basing our purchase on the American Ford website options and cancelling our order when the Australian specification was released and not matching our requirements). So much for Ford wanting to improve their customer's experience and yet substantially limiting Australian customer options even though these cars come of the same production line.
I did enquire to Ford Australia in July 2015 about the manual ecoboost diff ratio because it is apparently supposed to be 3.55:1 as per the performance pack but is listed by Ford Australia as 3.31:1. Did get a a return call from the sales department a few days later only to be told that the sales department didn't really have the answer (and clearly wasn't going to make any further enquiries). Also got another call about a week later to be informed that my car was on the production line on 9th October 2014 and delivery generally took about 3 months.
As per information I got from my dealer, the first four cargo ship deliveries are classified as shipment A and my car is in shipment B. He stated that they were supposed to get their first car around 18th December 2015 but as of 24th December they still hadn't got a delivery.
So apparently, Ford Australia can manage to deliver a Mustang to a radio personality by the 11th December and a Melbourne dealer already has a 'dealer owned' demo on the lot but alas, everyone else is still waiting. It's not that the deliveries have been delayed, that could happen to anyone, it's the fact that Ford Australian and it's dealer network appear to be a long way from improving their 'customer experience'. The Mustang release could be a huge marketing success for them but in what appears to be standard modus operandi for Ford Australia they appear indifferent to the opportunity.
I have since been given permission to also purchase a new MX-5 (my wife was actually the instigator, if you can believe that. I think she wants the Mustang to herself and unmodified). The dealer looked at their international database and gave me a delivery month (April 2016). If anyone one from Ford Australia is reading this, that is how simple the process should be.