Known as the Sydney West Metro Link, the consortium is on the cusp of lodging an unsolicited proposal for a metro-style rail line from Central to Westmead in western Sydney via Strathfield, Olympic Park, Camellia and Parramatta.

Under its plans, about half of the 26-kilometre line from Central to Westmead would be via tunnel while the remainder would run along existing rail alignments or viaducts.

Former state Labor treasurer Michael Costa said the window of opportunity for applying value capture – which typically involves placing levies on new homes and other buildings – to help pay for the project would close quickly because large parcels of land in a corridor between Olympic Park and Parramatta had yet to be redeveloped.

"Once the properties come to market or are developed under existing planning regulations, you lose the opportunity for a value-capture model," he said.

"This is a one-off opportunity to apply the value-capture methodology ... to construct, at reduced cost to the government's balance sheet, a high-capacity, frequent metro on the western corridor."

Mr Costa, who also served as transport minister, is acting as a strategic adviser for the group that includes Sydney developer John Kinsella's Billbergia, engineering group BG&E and design company Conybeare Morrison.

The consortium argues legislation will need to be passed to capture the value of land in the corridor between Olympic Park and Parramatta, and ensure the money raised is directed towards meeting the $10 billion-plus capital cost of the line.

It also needs the support of the government because the state owns large swaths of land in the corridor.

Transport Minister Andrew Constance said the government was "very keen to see what we can do in terms of value sharing above and beyond" its multi-billion-dollar investments in new metro and light rail lines in Sydney.

"We are very, very keen to work with the private sector and want to hear their proposals," he said.

Mr Constance said value capture was an important mechanism, and "if developers make a net gain off the back of the taxpayer-funded infrastructure going in, then we should share that gain to build more infrastructure for the future".

"The taxpayer benefits because ultimately there is that private-sector contribution," he said.

Mr Constance is on a 10-day trade mission to Singapore, Hong Kong, Shanghai and Tokyo where he is meeting major rail operators such as MTR, which will operate the first stage of Sydney's metro rail line between Rouse Hill and Chatswood.

The Sydney West Metro Link consortium is touting its plans as a solution to spending billions of dollars on upgrading the heavily used Western Line, as well as an opportunity to build major rail infrastructure at reduced cost to taxpayers.

Mr Costa said the corridor in western Sydney was one of few in Australia where value capture could be successfully used to pay for multibillion-dollar transport projects.

"This is probably the only corridor in Australia that lends itself to value capture," he said. "The avoided cost on the Western Line strengthens the economic case."

Under its modelling, up to 60 per cent of the first stage of a new metro line from Central to Westmead could be funded by placing levies on new homes and buildings.

The second stage of the project involves extending the line west to the new airport at Badgerys Creek, or east from Central to Kingsford, Maroubra, and La Perouse, where the government has said it is keen to sell Long Bay Jail.

The group cites the construction of a 300-metre bridge between the fast-growing suburbs of Rhodes and Wentworth Point near Olympic Park as evidence of value capture working successfully.

Bennelong Bridge opened in May, more than two years ahead of schedule, and was funded by four large landowners including Billbergia.

Billbergia spokesman Rick Graf said the Bennelong Bridge showed it was possible to create coalitions of landowners to enable infrastructure proposals to get off the ground.

Provided it can win government support, the group's ambitious timeframe is for the first trains to run on a new line between Central and Westmead by 2024, and by 2027 on an extension to the new Western Sydney Airport at Badgerys Creek.

The group is vying with a growing list of large investors and property developers to win state government backing for mega rail projects.

It has had preliminary discussions with councils, state politicians and bureaucrats ahead of submitting an unsolicited proposal within the next two months.

Critics say many of the private-sector proposals are pushed by property developers whose primary aim is to unlock housing development and enrich themselves, rather than build public transport where it is needed most.

The plans for new lines in Australia's largest city come on top of an audacious $200 billion proposal for a high-speed train line from Sydney to Melbourne via Canberra and Wagga Wagga.

The plan is spearheaded by Melbourne group Consolidated Land and Railway Australia, whose advisory board includes former state premiers Barry O'Farrell and Steve Bracks, and US former chief transport bureaucrat Ray LaHood.

The group proposes creating eight new cities and towns between Sydney and Melbourne, and funding the high-speed train through value capture.