The commission's initial hearing block is probing the circumstances of a two-day work stoppage on a major level-crossing removal project on Gap Road in Sunbury, northwest of Melbourne, in June 2022.
Work ground to a halt on the project on June 6 of that year after CFMEU delegates occupied the site, issuing dozens of safety notices, blocking machines and refusing to move even when police were called.
Operations only resumed after the union's demands were agreed to during a June 7 meeting, including installing their own union-aligned labour contractors and a health and safety representative, the inquiry heard earlier.
Despite WorkSafe being contacted during the stoppage, inspectors did not attend the site until June 8, after the dispute had been resolved.
WorkSafe inspector Quinton Drury told the commission on Wednesday, the situation at Gap Road was assigned the lowest possible level of priority.
Mr Drury explained issues were assigned a priority based on their risk to safety, rather than other impacts such as a work stoppage or delays to projects.
During the June 8 inspection only "minor" safety issues were identified, those being piling holes on site which were not sufficiently covered.
"Those issues were remedied at the time of our inspection," Mr Drury said.
Mr Drury said that in his experiences, tensions would arise between inspectors and union members if the safety notices they were raising were not supported.
"Tensions may rise if they feel as if they're not supported," he said.
"It could go a little bit south."
On Tuesday the commission heard from Joe Aygur from construction giant John Holland, which was the main contractor on the Sunbury project.
Mr Aygur told the commission it was unusually difficult to get WorkSafe to attend the site during the dispute.
In his experience of other similar situations, he said WorkSafe inspectors would typically attend on the same day an issue was raised, and generally within a few hours.
"We were struggling to get the WorkSafe inspectors to come out to site," he said.
"It was unusual."
Another John Holland employee Steve Testolin, also gave evidence to the commission on Tuesday.
Mr Testolin said he felt he and others managing the site received no support from authorities, including WorkSafe, police or the state.
"We were being left to fend for ourselves," he said.
"We needed the government representatives to take this up the tree to government and tell them what's actually happening."
