I’ve found out a bit about what NBN Co will want in new MDUs (ie apartments): NBN-NO-GDE-0011 section 6.2 says see NBN-TE-CTO-284 which says “Provision of a minimum of P23mm nominal inside diameter, white, rigid communications conduit with draw string, from either the telecommunications room or riser/closet location to each NTD location.” The NTD is the device inside each apartment that eg a router will connect to.
So separate 23mm (ca 25mm outside) individual conduits to each apartment is what they want.. and it may well turn out to be a similar requirement in existing MDUs! But that information still seems vague.
How to run those conduits at reasonable cost and impact (they might look pretty ugly) is what OC’s might have to decide unless other solutions that use existing cables (eg telephone cables) are eventually permitted.