The Australian Rail Track Corporation and Victorian government remain locked in negotiations over work needed to keep the track up to a class 2 standard.

Appearing before the Senate committee in April last year, former ARTC chief executive John Fullerton said the $235 million in federal funding to upgrade the line - due to be completed in 2021 - would be enough to complete the project, but not for ongoing maintenance.

His successor Mark Campbell was too sick to appear at the Estimates hearing this week, leaving ARTC head of strategy Simon Ormsby to answer questions from Senator Janet Rice.

Mr Ormsby described the negotiations as "still a work in progress", but "proceeding reasonably".

"The project works, as best I understand, are scheduled for mid next year, and we'd expect to have a better position towards the end of this year," he said.

"It's not really a hold-up. We're just working through the scope that's required with Victoria."

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He could not answer another question from Senator Rice, who asked "how long before the line degrades to its previously completely unacceptable condition?".

She also asked if the ARTC had asked the federal government for maintenance funding.

"We run a commercial enterprise, and, typically, when one of our customers seeks a higher track standard, they would have a commercial resolution around meeting that additional cost, so our discussions are with the Victorian government," Mr Ormsby said.

"ARTC does contribute maintenance funds to that corridor as well."