A Railtrack spokesman said a formal announcement was due within a week.
While contracts have not yet been exchanged, Mr Corbett is set to succeed John Edmonds, Railtrack's present chief executive.
Railtrack confirmed last week that Mr Edmonds was to step down early. Just days later, Mr Corbett announced he was to leave GrandMet.
His departure had been expected after his opposite number at Guinness, Phil Yea, secured the job of finance director at GMG Brands, the new company to be formed by the proposed pounds 23bn merger between GrandMet and Guinness.
A spokeman for GrandMet said yesterday: "Mr Corbett has had talks with a number of people, including Railtrack. But no formal offer has yet been made." It is understood that contracts will be exchanged imminently.
Mr Corbett received a pounds 600,000 payoff from GrandMet. It is thought Railtrack will have offered him significantly more than the pounds 136,000 basic salary Mr Edmonds took home in 1995/6.
Spencer Stuart, the headhunting firm, was briefed some time ago to seek a replacement.
Sir Bob Horton, Railtrack's chairman, is said to have been keen to replace Mr Edmonds with someone with a wider commercial background. Under Mr Edmonds' leadership Railtrack has become embroiled in some high-profile disputes with the rail regulator, John Swift, QC.
Late last week, after a crisis meeting with Mr Swift, Railtrack completed an embarrassing U-turn by agreeing to alter its licence to include promises on spending committments.
Mr Swift had threatened to take the company to the Monopolies and Mergers Commission if it failed to make watertight promises on a pounds 16bn 10-year investment programme for Britain's railway network.