imagine if this was telstra, page-16

My understanding of the ACCC process is they must first determine if the market is competitive, if they determine it is then they have very little leeway to do anything. If they determine it isn't then they look to see if there are barriers to the entry of competitors, if there isn't then again they have little leeway.

So they would have to find the market noncompetitive and/or there are barriers to entry. This is where they could make a determination.
But it can't be a blanket ruling across all regional areas as if there are two mobile providers in say Hay, NSW then there is competition, so no idea how they would get a ruling that would pass the reasonable test or even apply natural justice.

I find it sad that after Vodafail lost approx 30-50% of it's customers due to not investing in its network, they may now not have to invest a cent to get a reliable network across the nation.