Hi @Lucygirl . Find an ACMA licensed cabler in your area and ask his opinion. You want to reclaim the connection box on the house and the cable from the house to the overhead cable. Is he able to do that? Maybe also the coax cable inside the house.
If you have overhead electricity cables, your rebuild might use a "private pole" for electricity supply into new house. Ask if the HFC coax cable can use that pole to go underground into the house. If it can't, the cabler should indicate to the builder what is required (maybe just a second pole and an extra duct underground).
This issue is addressed here, but there was no definite answer.
@Lucygirl . Another thing to consider in rebuild. Can the coax cable run directly to the Arris NBN box or does it need the equivalent of the external connection box, which runs to the coax wall plate and the Arris? Consider where you want the wifi router. Somewhere central. If two storeys, a wifi extender might be needed. Consider laying Cat6 ethernet cables from each room back to some point with a patch panel (coax cable wall plate goes here); allows a remote ethernet connection or cabled wifi extender. Are you getting solar panels with smart converter using wifi for management? CCTV cameras? Granny flat could have its own ethernet cable into main house.
Hi @Lucygirl, ISPs are just resellers of the NBN services.
Therefore, for line repair or any works that involves the line outside, this needs to be raised to NBN Co. as only their technician alone are allowed to work on their line and/or infrastructure. You may try to confirm with NBN Co if they will allow you to hire a private tech instead.