The $1.5 billion "Tarneit link" would run through new housing estates and paddocks between Werribee and Deer Park.
The new rail line — flagged in Sir Rod Eddington's $20 billion transport plan in April — is expected to be included in a government transport statement to be released in the first week of December.
Construction of the line would result in Geelong trains travelling through Sunshine instead of Altona, before reaching central Melbourne.
Premier John Brumby met last Thursday with Mr Eddington, who this week will take receipt of a confidential Brumby Government submission to Infrastructure Australia on the state's transport funding needs.
Mr Eddington chairs Infrastructure Australia, the body advising the Federal Government on how it should spend its $20 billion Building Australia Fund.
The Tarneit rail link could result in new stations being built in growth corridors including Derrimut, Truganina and Wyndham Vale, according to the Department of Transport.
The department has repeatedly discussed the rail link with Wyndham Council and residential developer Dennis Corporation.
Much of the land the line would travel along is outside the Government's urban growth boundary — although property groups are lobbying for the boundary to be extended westwards.
Wyndham Council is backing the plan, saying it would get V/Line trains, frequently delayed between Werribee and North Melbourne, out of bottlenecks.
Dennis Corporation chief Bert Dennis, whose company owns residential land throughout Wyndham Vale that would jump in value if the line was built, said he had talked with the Government earlier this year.
The new link would mean only metropolitan Connex trains would operate on the Werribee line, while express V/Line services from Geelong would join the Ballarat line.
Critics of the proposal argue it will only move the problem of bottlenecks with Connex trains on the Werribee line to the Ballarat V/Line route.
The critics also argue it is a longer route, and will remove any time savings for Geelong passengers created by the fast train project.
Wyndham, which takes in Werribee, Point Cook and Hoppers Crossing, has very poor access to public transport.
More than 65% of its residents work outside the municipality but, according to the Government's 2008 Transport Demand Atlas, just 15% use a train or a bus to get to work.
In Boroondara, which takes in Camberwell, Hawthorn and Kew, 36% use public transport to get to work.