Free rail travel across Sydney this weekend to head off mass disruptions could cost taxpayers up to $3.5 million in lost revenue.

Transport authorities' pay negotiations with the Rail, Tram and Bus Union (RTBU) broke down earlier this week and the union threatened to disrupt services on one of the busiest weekends of the year.

In a bid to ease weekend commuter chaos, with major football events scheduled, Transport Minister Jo Haylen on Thursday announced rail travel would be made free this weekend.

Thomas Costa from Unions NSW told ABC Radio Sydney on Friday the planned action on the trains to football stadiums would be called off.

Transport for NSW secretary Josh Murray RTBU has made about 250 claims. Some of these include having drivers on driverless metro services, the conversion of the T3 Bankstown line for the metro and slashing some train fares to 50 cents a trip.

A spokesperson for Transport for NSW said based on weekend timetable data the estimated cost of foregone revenue from fares would be between $2.5 and $3.5 million.

"People using NSW TrainLink services will be refunded and anyone with footy tickets will have free access."

A spokesperson for the transport minister said the cost would still pale in comparison to what has already been spent on the Southwest metro project.

The Bledisloe Cup match against New Zealand on Saturday afternoon also pressured officials to make a deal with the RTBU.

"The reason for the government offering free travel this weekend is to get the union to lift their bans relating to the T3 metro," the spokesperson said.

As a result, the union has agreed to not stop work or construction on the T3 Metro line this weekend.

A Transport for NSW spokesperson said those travelling on other parts of the network where strike action was ongoing could still expect delays.

"Due to the unpredictable nature of industrial action passengers should also be aware that services may be cancelled at short notice, so our advice is to please listen to station announcements and work with Transport staff on the ground," Transport for NSW said in a statement.

"Fans heading to Moore Park for the AFL and NRL double header on Friday were warned to expect major disruption — particularly on the T4 Eastern Suburbs and Illawarra line."

Track work that was planned for this weekend on the T2 Leppington, T5 Cumberland, T8 Airport and South and T3 line has been postponed due to the industrial action.

Replacement buses which were planned between Campsie and Lidcombe for T3 line track work will continue to run on the weekend, alongside trains.

All bus, ferry and light rail trips will be charged and commuters must tap on and off as normal.