It's a bit hit or miss. Mince is made from the meat that can't be made into sensible cuts of meat, and will thus have a fair amount of fat no matter what. Check the labels on packaged mince, or ask your butcher.
Perhaps it would be best to have your butcher mince a lean cut of meat, it's more expensive, but at least you're not then paying for fat and water. It's for precisely this reason that now only mince I ever buy is kangaroo due to the much lower fat content.
I did a search for the official Australian Standard definition for "lean meat". There is none, yet, but Food Standards Australia has the following law proposed (obviously not complied by everyone):
"Mince must be made from minced whole meat (ie the only fat allowed is that attached to a piece of meat). Where a claim is made such as premium or lean mince then the percentage of fat must be declared."
One other thing you could do regardless of its fat content is cook the mince till it goes brown then sit it in water and scoop off the fat that floats to the top then put it back in the pan or pot and continue to cook it.
The Whirlwind Australian telecoms forum has a good thread regarding fat in mince:http://forums.whirlpool.net.au/archive/1680994