In our building, electricity is individually metered for each lot, so is the gas. So it should not be any more onerous for Sydney Water to come out and read individual meters if they are installed. The added cost to read a meter would only be a very small percentage of the total cost we get slugged. Like electricity, there would be a separate meter to record common property usage, which the OC pays but includes in levy estimates.
I think individual water meters are now required on new developments, but retro-fiiting them into existing buildings would be extremely difficult and expensive.