They've changed the selection as of late to throw out the computer-based assessments. It now goes:
PHASE TWO
Group discussions of various subjects, some controversial (Legalisation of Marijuana - Is the war in Iraq Just - etc.). They're looking for how you interact with others with different opinions, not what your opinions are.
Written exams (numeracy and technical knowledge papers).
PHASE THREE
Group exercises (bridge building; wrecked off an island scenario). Again they're looking at how you deal with team working.
Personal interview - about 45 minutes. Mixed reports on this - some report how relaxed the interview was, some say it was too relaxed and they gave away a bit too much, I personally felt I got a real grilling. Be prepared for this, with an interview coach if you can - I thought I was, but I wasn't and fluffed it.
Best of luck!