which Universities in Australia have good post graduate Engineering programs?

Answer 1

All the major Universities have good post-grad Engineering programs. Different universities tend to specialise in different areas so it would be worth checking out the Engineering departments . The top 12 Universities in Australia are:

ANU
Uni of Melbourne
Uni of Sydney
UQ
Monash U
UNSW
Uni of Adelaide
UWA
Macquarie U
QUT
Uni of Wollongong
RMIT

but there are others further down the list that have good engineering programs. The list of all the Australian universities and links to their programs is here:
http://australian-universities.com/list/

Answer 2

Different universities have different policies for each degree. For Australian universities, postgrad diplomas are often similar, but without the research component. Also, you might find that one of them is not accreddited while the other is- a psychology degree might allow you to become an licensed psychiatrist, but a graduate diploma might not be. The best way to find out would be to ask the university you are applying to- there should be an honours or postgraduate coordinator who will be able to tell you the difference.