Yes, I'm in Oz.
The situation is that there is one 850MHz network in Hong Kong, so Samsung markets this phone as quad band 3G (850, 900, 1900, 2100).
There are two 850MHz networks in Oz: Telstra NextG and Vodafone 850.
I've emailed Samsung HK support with the information obtained from the service menu in my phone.
The firmware is I8150ZSLM4 which is a Taiwan firmware. This phone is marketed as a dual band (900, 2100) 3G device in Taiwan. I think Samsung HK made a mistake, either by using Taiwan firmware or marketing it as quad band 3G. Taiwan firmware might not support 850 and 1900 bands.