According to AAMC (the MCAT test maker), there are 2 MCAT test centers in Australia. Most testing centers are located inside a college or university. You can select a testing location that is nearest to you. Please note that you are able to choose a test center when registering for the MCAT.
UNIT 3, LEVEL 8, 20-22 ALBERT ROAD
MELBOURNE, Australia 3000 VIC
ITIC PTY LTD LEVEL 3, 321 PITT STREET
SYDNEY, Australia 2000 NSW