Thank you to all who replied.

It turned out that the landlord was the hero in the end and stood his ground with telstra saying that no excavation was required. He asked if he could try putting the replacement wire through himself and was successful. The line now works with no problems and my respect for our landlord as a handyman has grown.

This all happened a while ago, has just been a long time since I have checked here. Thanks again to all who replied!

PS The line WAS already in the house and was advertised as a working phone line. We had just never tried to have it connected until recently seeing as mobile phone caps are a decent alternative to land lines now…