The NSW Independent Commission Against Corruption started public hearings in July into alleged rigging and inflation of contracts involving former Transport for NSW procurement officer Ibrahim Helmy between 2012 and 2024.
Mr Helmy is scheduled to give evidence for several days, beginning when hearings resume on Tuesday.
He was arrested in September and detained to appear before the corruption watchdog, but has not been criminally charged.
The 38-year-old had been missing since May, when he failed to show up for an examination before the NSW Crime Commission.
The commission held his Australian passport when Mr Helmy was detected at Sydney Airport awaiting a flight to China in September 2024.
Computers and storage devices were seized along with a US passport, before Mr Helmy was released on conditions.
But he failed to return from putting the bins out one Sunday night, according to his family, who did not report him missing, previous hearings before the corruption inquiry have been told.
The alleged kickback scheme involved contracts being inflated, with contractors splitting the extra funds with transport officials, making payments in cash, cryptocurrency and gold.
Mr Helmy was terminated from the agency in February.
He is suspected to have received more than $11.5 million from the alleged scheme, which involved contracts worth more than $343 million.
It is alleged Mr Helmy formed corrupt relationships with several other agency contractors and colleagues over the years when the scheme was underway.
The most recent hearings in August took evidence from Peter Le, a procurement and contracts officer accused of "actively" collaborating with Mr Helmy.
The probe is the fourth public inquiry since 2019 into claims of corruption in procurement at Transport for NSW, which is responsible for a $23 billion annual budget.
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