I've worked here for 15 years as a civil engineer and I have never seen the civil construction industry so busy as it is now.
If you have a recognised degree (not all overseas degrees are recognised as engineers in AU), you'll be able to find something relatively easily.
If you do have trouble finding something, you could try a 3 month internship, work your backside off and you will get a job at the end of it (if you're good). Otherwise, you could also try the major recruitment companies (most engineering firms use recruiters because of the amount of junk overseas applications they get when they advertise themselves... best to pay someone else to sort through the rubbish).
The pay here is pretty good also compared to elsewhere (though it's really hurting margins on projects).
Beware, Sydney is EXPENSIVE to live in though...