> The ISP doesn't need to know what the content is or be pro-actively looking for content.
Sure, be it a torrent or pornography, the ISP doesn't have to care in Australia.
> The rightsholder would look at the connecting IP and then contact the owner of that IP for if that IP was allowed to view age-restricted content.
eg: Hollywood Inc. would contact the ISP to ask for details about the customer using that IP address at a particular time.
The existing court ruling establishes that the ISP has no obligation to provide customer details to Hollywood Inc. or to any third party provider of (say) pornography.
Also, typically an ISP customer is a household that contains adults, children, relatives, boarders, passerby's that use the router Guest account, etc.
So, not only is the ISP not obligated to provide customer details, those details are most likely those of an adult over the age of 18 as 12 year olds rarely have an account with an Australian ISP provider.
The rightsholder would look at the connecting IP and then contact the owner of that IP for if that IP was allowed to view age-restricted content.