Indeed. The compositing tool of choice for this movie and any other effects-heavy movie from the late '90s well into the 2000s was Shake (by Nothing Real, later bought by Apple). The only competition was Nuke, the in-house tool at Digital Domain. It is the last one standing today, since Apple gave up on the high end.
Interesting anecdote I heard: Shake was up for an Academy Award, but Apple pissed off the wrong customer when they discontinued the Windows version (which was used for The Matrix). I won't name the post house, but the owner reportedly sat on the academy's technical committee and tanked Shake's nomination as punishment. Kinda sucked for the team, who of course were blameless.
There was a surprising amount of set dressing done. Some people have pointed out before that they must have put down fake tiles as the direction of the tiles in the film are diagonal (I think) instead of checkered. But as other people have said, Sydney was very run down in the 90s and many buildings were genuinely just like that. It's come a long way.
I was there two years after it was filmed. It was not that run down, not by a long shot :) And I lived in a pretty bad area (I used to leave my car unlocked because the heroine junkies would smash the window to have somewhere to sit while shooting up). I guess some of the cleanup was for the benefit of the olympics but that doesn't apply to the back street stuff.
