Modelling calculating the cost of a two-week shutdown of the NSW train network was just “contingency planning”, the treasurer says.

Matt Kean has told a budget estimates hearing that he found out about last week’s 24-hour shutdown of trains on the front page of a newspaper.

Premier Dominic Perrottet and Transport Minister David Elliott both said last week that was where they first learned of the train shutdown too.

“Governments plan for all kinds of scenarios”, Mr Kean said on Monday.

But he said he wasn’t briefed on that specific contingency planning.

Treasury Secretary Paul Grimes said he too “had not been aware of the scenarios that were being considered by the chief economist”, who had compiled modelling showing a two-week shutdown of trains could cost the state $350 million.

The plans were made days before commuters woke up to a city with no trains operating, on the same day as Australia’s borders opened and international tourists began arriving at Sydney Airport on February 21.

Transport for NSW did not believe the train network could run safely while union workers refused to work altered rosters and a decision was made to suspend all services.

The modelling conducted the week before was used to support a Fair Work Commission action and came amid planned industrial action by rail unions who are negotiating a new enterprise bargaining agreement.

Mr Kean said he first read the affidavit from Chief Economist Stephen Walters to the commission as he prepared for budget estimates last week, days after the train shut down.

He explained that Mr Walters testified he had believed trains could shut down due to the cumulative effect of ongoing industrial action but it was only “scenario planning”.

“There was nothing specific and he was providing general advice,” Mr Kean said.

“It’s entirely appropriate that we would do contingency planning for all scenarios, just like we did”.

Asked at the hearing whether he should be told about a “$350 million problem looming”, Mr Kean said “it would be useful to have that information if there is a serious risk of a particular scenario occurring”.

Greens MP David Shoebridge said shutting down trains was “never the union’s plan”.

“The only way this kind of disaster could happen was if your government shut the trains itself,” Mr Shoebridge said.

Mr Kean replied “the only way this disaster happens is because the union movement compromises the safety of train commuters across the network, and that’s something that we never ever want to see happen again”.

Trains resumed on their full timetable with close to 3000 services operating on the Sydney Trains network and close to 400 on NSW TrainLink regional services on Monday, Transport for NSW said.

“Sydney Trains and NSW TrainLink apologise for the inconvenience faced by commuters last week and we are committed to continue working with our employee groups to ensure we return to being a world class transport system,” Sydney Trains chief executive Matt Longland said.

Further meetings will be held this week, Mr Longland said, and “contingency planning” was in place.

– AAP