But the company behind the $200 billion, 35-year project can't yet specify the route for how its first stage - to the Shepparton region - would be reached in a promised 30 minutes.

A magnetic levitation rail system is the preferred option for the line, which would be built from the profits of farm land bought dirt cheap and sold for hundreds of times its purchase price – once it was turned into a residential city, accessible by fast rail.

Consolidated Land and Rail Australia's chairman and co-founder is Nick Cleary, a New South Wales real estate agent from Bowral and a one-time federal election candidate for The Nationals.

Former Victorian Premier Steve Bracks and former NSW Premier Barry O'Farrell on Thursday helped launch the company's speculative rail line plan.

"I know there is cynicism about this because of the previous attempts over the last 20 years, but it will happen - it has to, and this is the best proposal for it to be achieved," Mr Bracks said.

The proposal is as much about land speculation as transport: it proposes eight new regional "smart cities" near existing towns, that would be connected to big cities with high-speed rail.

"This is a decentralisation plan and an inland cities plan," Mr Cleary said at Thursday's launch. "It's about land value capture that will help to pay for the civil [works] and the rail infrastructure."

"It can work because we can take farmland for $1000 a lot and turn it into a residential allotment of some description [worth] about $150,000. That uplift - between $150,000 and $1000 - gives us the capability and capacity to fund the civil and rail infrastructure."

Asked where the train would leave from in Melbourne, Mr Cleary said: "Our aim is to take it to the centre of Melbourne".

Asked where it would arrive near Shepparton, he declined to say "out of respect to landholders" that had signed legal options, that last for four years, over land near the town.

He said the finer financial details of the project were commercial-in-confidence and could not be revealed. He speculated that ticket prices would be in the "ballpark" of 10-to-23-cents-per-kilometre.

The CLARA consortium met Prime Minister Malcolm Turnbull in March.

The Greens transport spokeswoman, Senator Janet Rice, said a fast rail line between Melbourne and Sydney was essential, but that it was infrastructure the federal government needed to provide.

"We think value capture could have a role to play, but we propose that smart use of government debt from a national infrastructure bank is likely to serve the interests of the Australian community more," she said.

She said the lack of information provided by the consortium behind the proposal was troubling. "Being asked to 'just trust us' is not good enough for a project of this scale," she said.