I am in townhouse so we don’t have this sort of arrangement but I understand from friends in apartments that it is usual for hot waters to be record each unit’s consumption. Then the total energy consumption (usually gas) is measured and a conversion factor is calculated to convert litres of water into MJ of gas. The conversion factor varies a bit for various reasons including that it takes more gas to heat the water when it is colder in winter.
If the retailer is not reading the meters, then the OC could. If the OC did this, then I would have thought that the gas or electricity used in each unit behind the single meter of the OC would be regarded as an embedded network. The Australian Energy Regulator has strict rules about energy supply to ‘premises’. The OC might be able to take over the meters, even if it is required to install smart meters that enable peak demand or time of use tariffs. Then the OC might negotiate a cheaper deal with the retail who only has to read one meter. The OC could read the individual meters and charge people according to their usage including their varying peak and off peak consumptions. That would enable some to respond to the price signal and avoid peak demand while others who can’t be bothered to run the dishwasher a bit later can wear the cost personally without imposing it on everyone else.
BTW. Electric vehicles are not regarded as premises so the rules are not as strict.