Yes it has been discussed before. ESC became mandatory for new cars in Victoria from 1 January 2011. Other states are 1 November 2011 I believe, although I don't see manufacturers pushing different models for different states, so apart from old stock I would guess Victoria either isnt selling any new cars (not) or this makes the ESC situation effectively current now for all states by default, if not by law.
ICV's in Victoria are exempt from the ESC requirement (according to the VASS engineer I spoke to) in a similar fashion to how they are exempt from the crash testing requirement. Although, I don't believe that you need to display a "this car has no ESC" sticker in the same fashion as you are required to display a "this car has not been crash tested" sticker in a visible fashion.
Here is the previous discussion thread:
ESC mandatory