As a fully qualified Airline trained Aircraft Maintenance Engineer - Engines and Airframes (I went to University to get a degree instead of going down the LAME route) I think that in todays (after dealing and training many apprentices and adult trainees alike) world you will require more than just 4 years hands on without any sort of formal training before you can actually become licenced.
As all Aircraft trade training is now done under the National Aerospace Curriculum and also requires you to have a completed NAC Journal - a formal document that you keep all your work history in, which also has requirements related to the types of work you do, the systems you are required to gain experience in - with minimum hours on each system. This SOE (if you like) is required to be signed off by an approved AAA assesor, and you are also assesed along the way. This is a very basic explanation of the hands on training that goes towards obtaining your Certificate IV in Aeroskills (old school it was an AME).
You are also required to study the theory/tradeschool component, and these courses can be done through places like Aviation Australia, where you dont need to be employed initially, but you do study 12 months full time theory and then if successful they will help place you into employment to gain your hands on experience. We have had many apprentices through these guys and some of them are adult or mature age people.
Gone are the old days of just getting some basic hands on and passing a few exams, and I think you will need to scour the CASA site a bit better for the correct information, but I do know that you will require a formal Certificate IV in Aeroskills before you can become a LAME now, as I wouldnt employ anyone without one.
I was one of the last groups of apprentices (1993) that actually got trained the 'old-fashioned' way with block release trade school and hands-on on the job training - CASA and the ALAEA want the industry (understandably) a lot more professional, therefore weeding out the cowboys that are out there.