At the risk of turning this into a rail forum, I wonder if a less ambitious rail project might have been the way to go. Tilt trains which run on current but slightly upgraded track, as in Europe could be done for less cost. Canberra to Sydney in a tilt train, with a journey time of two hours is not bad. A 7am departure from Canberra station, into Central at 9am, with time to reach a 930 meeting in the centre of Sydney is good. Four hours between Canberra and Melbourne is reasonable, and six hour Sydney to Melbourne is OK.