I converted my FAA ATP to a CASA ATPL a couple of years ago. It's not really that difficult as CASA aren't as illogical as the JAA but here's what you have to do:
Commercial Air Law Exam - Deals with Rules of the Air exclusive to operating in Australia.
ATPL Air Law Exam - Deals with Rules of the Air when operating over water and in international airspace.
IREX (IR Exam) - Self explanatory.
Don't expect to be able to pick up a self study guide like we can here. Firstly CASA doesn't publish the questions and secondly where as there's a simple easy to understand FAR/AIM here. There are some fairly hefty "door-stops" in OZ. The CAR's CAO's etc.
The IREX is, to put it bluntly a f**ker of an exam. You CANNOT pass it by self study, in fact the failure rate is about 60-70% of first attempts. It's about 30-35 questions and you have 3 - 3.5 hours to do it in and you'll need all of that time. Most flight schools and the Uni's run IREX courses. I know a good school in Brisbane but can't help with anywhere else.
Once you've completed the exams you can start the flying, which consists of a CPL flight test and a Command IR flight test. Be prepared to pay a fair whack for it though. While renting an aircraft isn't too much more than it is here, you have to pay for anything connected the the airpsace system. Eg: filing a flightplan, the amount of time you're on an airway, shooting an approach and of course every time you land, you have landing fees.
There is a major caveat though to converting your FAA ATP. By converting, you bypass about 6 of the ATPL theory exams. Your CASA ATPL will look the same as someone who didn't convert it but when you come to apply for a job at Virgin Blue or Qantas, they'll ask if you have passes in ALL the ATPL exams. If you have converted, you haven't. Qantas won't interview you, Virgin Blue will but will expect you to do the other exams you weren't required to do in the 1st place. Oh, and then if they do offer you a job, they'll expect you to do a Southwest and pay for your type.
And just when you thought it couldn't get any worse, there's more; if you do decide to do the exams you weren't required to do in the 1st place but fail one. CASA will down-grade your new ATPL to a CPL until you have passed all the exams.
Pilot was on that list lat time I checked. But, you have to poke around on their immigration site yourself but on there somewhere (either on that page or somewhere on the CASA site.) It says that since that there are so many aussie pilots out of work they were considering removing the pilot occupation from this master list of needed occupations.
I'd love to ditch all this bull$hit in the states and go fly in oz. But apprently, they have their labor problems too and it's not really worth it to go through the conversion process.
You had some useful information in your post but it's not all true. A good friend of mine did all his flight training in the US and worked for skywest for a couple of years before deciding to move back to Australia. He is now working at QANTAS! If you like you can pm me and I will forward you his email address so that you can get in touch with him and ask him how it went.