It would likely be the Government sued and as in most cases, settled out of court. Telstra nor the Government like adverse publicity and presuure to settle would be immense.
If any victims families were after justice and not money, then I am having trouble in agreeing that the families would be happy to settle out of court, under any circumstances. Not if the whole purpose of any legal action, was to attempt to publicly expose those partially to blame, for not assisting contribute to preventing crimes committed after the initial crime(s), or discovering the CSK earlier and saving the families from drawn out suffering, from such a long period before any CSK was caught and successfully convicted.