Victoria Police was notified of the incident but did not attend, a police spokesperson said.
The firefighters union said the visit was vital for firefighters’ knowledge of the tunnel should they need to respond to an emergency, and that they had entered to conduct a “building inspection” and to examine a Fire Control Room and related equipment.
“Whatever political finger-pointing is happening, firefighters are still doing their job,” secretary Peter Marshall said in a press release. “Firefighters’ job is to make sure they know what to do if they ever need to rescue you.”
Marshall rejected any suggestion that he directed members to disrupt the new rail line.
“I didn’t even know this had happened until the media rang me about it,” he said.
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Marshall and the union are campaigning against the government and have claimed firefighters do not have suitable equipment to respond to emergencies in the Metro Tunnel and West Gate Tunnel toll road, which is due to open next month.
The trespassing incident triggered minor glitches on Sunday, including passengers being unable to board one train at Anzac station.
Platform screen doors at the new Metro Tunnel stations can only open if a train stops in perfect alignment, made possible by the new high-tech signalling which automatically guides trains through the tunnels.
Metro Trains CEO Raymond O’Flaherty said that trains had to operate under drivers’ control following the intrusion, and in this case, overshot the platform.
“We’ve been running empty trains through here. Now, for the first time, they’re full of passengers,” O’Flaherty said.
“We fully expect to see these glitches along the way as we build our confidence and get ready for the first of February.”
Metro Tunnel trains will only operate between West Footscray and Westall every 20 minutes from 10am to 3pm on weekdays until February 1, when a full timetable will commence.
Just under 75,000 people rode the Metro Tunnel on Sunday, with more than 22,000 coming through the new State Library station and 16,000 visiting Town Hall.
It was a more subdued affair on Monday, with the tunnel’s limited “soft launch” timetable making it of little use to most commuters until February 1 but still attracting curious sightseers.
Teddy Nethersole had a pupil-free day at school and was busy touring the Metro with grandma Martina Kooloos.

Teddy Nethersole at State Library station with grandmother Martina Kooloos.Credit: Justin McManus
The eight-year-old was a big fan of the orange arches at Town Hall station, as well as the glass platform screen doors.
“It’s so people don’t walk onto the tracks … they open automatically when trains come,” he explained.
Chris and Niki Holland from England are paying a visit to their daughter Emily, who lives in Melbourne. All three were impressed with the design of the State Library station.
“I do love the architecture in Melbourne, and especially the art deco style. You look up in Melbourne and you always see beautiful buildings,” Emily said, pointing out the distinctive 1920s-style lights and other fittings above the platforms.
Niki agreed the new stations captured Melbourne’s style. “It does reflect the sort of style that Melbourne has; the contemporary feel, the openness, the airiness,” she said.
John Cahir meets up with a group of fellow ex-Bureau of Meteorology colleagues every Monday for a decent walk (about 10 kilometres, usually) somewhere around the city.
Today, they decided to travel through each of the Metro Tunnel stations, starting at Town Hall.
“We’ll visit the five stations and then walk up to Brunetti’s in Carlton from Arden,” Cahir said. “It’s fabulous.”