After reading back through this thread, I have to admit that I got somewhat side-tracked (shunted) up another path and apologies to those with whom I had some disagreement.
The original news item was about business and development groups calling for a High Speed Rail (HST) link between Sydney and Canberra. On its own, it's clearly not feasible, with such a small potential patronage and financial return in relation to the cost, as RTT pointed out. As part of a broader High Speed Rail system between the major capital cities on the eastern seaboard, then that's an entirely different matter. Even then, it would be many decades before this would be feasible, if ever.
Where we diverged from the debate was to suggest a more realistic goal of upgrading the existing track at far less cost to a Medium Speed Rail (MSR) standard, allowing speeds up to 200km/h. You can use the analogy of the upgrading of the National Highway Network between Melbourne and Brisbane from the slow single lane goat tracks that they were to faster and safer dual carriageway standard, which has almost been completed. In fact I've just driven from Sydney to the Sunshine Coast and back and the final section to dual carriageway standard between Grafton and Ballina will be completed next year. Imagine what could be achieved if a similar commitment was made by the State and Federal governments to upgrade all of our main interstate rail corridors. It doesn't have to be up to "High Speed Rail" standard (350km/h+).
In relation to the Sydney-Canberra corridor, the population of Canberra is large enough to warrant an upgraded faster and more frequent rail service. This could be achieved by upgrading to a Medium Rail Standard with the elimination of excessive curvature and in the process shortening the route and allowing for higher average speeds. If a journey time of around 2 and a half hours could be achieved then it would be more than competitive with travel by car and coach.
Vienna to Salzburg fastest train time is around 2.5h for the 295 km journey or 118km/h. If its good enough for the Austrians its good enough for the Australian's.
So before starting such a project you need to deal with the highly complex and political issue of naming. As all great projects need a name, lets call its "Eastern Inter-capital 100", I've just saved many hours of $100,000's of public servant meeting time.
The project scope being that the XPT between Brisbane and Sydney and between Sydney and Melbourne as well as Sydney to Canberra can undertake the journey with an average speed of 100km/h or greater for regular express services. The upgrades will be done over 5 years, knocking off the biggest bang for your buck first and working their way through the various upgrades, realignments and improvements. Realignment is done to 200km/h, but train speed limited by XPT to 160km/h
Was does average 100km/h achieve
- Syd -> Mel, ~8-9h travel time
- Syd -> Can ~3h
- Syd -> Bris ~9-10h
Phase 2 "Eastern Inter-capital 120"
- Syd -> Mel, ~7-8h travel time
- Syd -> Can ~2.5h
- Syd -> Bris ~8-9h
This is achieved with further upgrades, but also new 200km/h rolling stock.