The revelations put the halt decision, which has caused chaos for more than 150,000 commuters, more than two hours before the first train was canceled at 00.48am on February 21, despite previous claims it had been made after midnight.

In a timetable presented at the hearing, Ms O’Neil reportedly told Mr Elliott’s chief of staff that the trains could not run safely or reliably and asked that the network could not operate under these conditions . She said the support was confirmed.

A later text from Mr Elliott’s chief of staff said the minister had been briefed and was comfortable with ‘our position’.

But Mr Elliott claimed he was told the department would simply renew its request to end the industrial action the following morning and that a halt was not mentioned in the appeal to his chief of staff.

Although he admitted he had been told there would be “massive disruption”, he said it was not unusual and he did not inquire about the nature of the disruption.

“I was waiting to get up at 4 a.m. to find out what a massive disruption would look like,” he said.

When asked why he hadn’t phoned Mr Elliott about the closure, Mr Sharp said written notice would be sufficient, but conceded that ‘in the end it would have been a useful part of the communications suite”.

Mr Sharp told Estimates he requested an urgent meeting with Mr Elliott on February 11 over the union’s planned action – 10 days before it was to start – but never got a response, even after pursuing his request a few days later.

The first briefing did not mention the shutdown

Sydney Trains conducted a risk assessment of the union’s planned action on Wednesday February 16 and the following day leaders decided the network would have to be closed if all bans continue.

Layoff risk formed the basis of the department’s application to the Fair Work Commission for dismissal.

However, during a briefing on the case on Thursday February 17, Mr Elliott said the department had never mentioned the network might be shut down.

And this despite the fact that the New South Wales Government’s Chief Economist has modeled the economic damage of a network shutdown to support the app and the Department of Health has provided evidence of the consequences for hospitals.

“We were not advised of a shutdown until 1:30 a.m. on Sunday morning, nor as an option,” Mr Elliott said.

“Obviously [if I had been told it was an option] I should have raised that to the Prime Minister. Without interfering with the decision, I would have tested it.

Sydney Trains CEO Matt Longland said at Thursday’s briefing “we discussed the importance of the action and what we were trying to do to prevent the action”.

“I don’t recall any discussion of the full shutdown or presentation of a risk assessment at this point.”

That Saturday, the union and Sydney Trains reached an agreement to withdraw most of the industrial action, but to maintain the amended work ban, which means workers only work shifts defined without change.

But an 11am disagreement over the slates agreed as part of the deal – which would have ramifications for the union’s work ban – saw Transport for NSW backtracked on safety grounds late on Sunday evening.

Mr Elliott insisted it did not matter that he had been told of the closure as it would not have changed the outcome.

“We are not in a position to question a safety assessment.”

“The circuit breaker strategy remains”

Unions had speculated that the shock stoppage could have been a Qantas-style IR strategy, referring to the 2011 dispute where the airline grounded its planes in response to industrial action to bolster its redundancy case.

Labor MP and shadow treasurer Daniel Mookhey pointed to text messages from Mr Sharp, who was a former Qantas executive at the time, to suggest a shutdown strategy was still in the works.

Mr Sharp had sent on February 22 to the Secretary to the Prime Minister’s and Cabinet Office, Michael Coutts-Trotter, that NSW Transport was withdrawing its termination package as it did “not meet the hurdle with some services running”.

Mr. Sharp’s text adds that “the strategy of the circuit breaker remains. Go vote in NSW Trains and look for mechanisms to get to FWC on Sydney Trains. This is not an easy step, happy to discuss”.

However, Mr Sharp told the estimates that the circuit breaker was aiming to seek conciliation with the commission.

Mr Mookhey replied that it was “not plausible”, given that conciliation could be achieved with a simple telephone call.