The NSW government is headed to court in a bid to block union plans to deactivate Opal readers at train stations as part of an ongoing industrial stoush.
A section 418 application has been lodged in the Fair Work Commission to have the "destructive action" to turn off or short circuit the machines from Wednesday declared unprotected, Transport Minister David Elliott said.
The move follows legal advice received by the government that the proposed action is prima facie unlawful, he said in a statement on Saturday.
"Sydney Trains and NSW Train Link believe the notified action is also unsafe and could cause financial impacts on commuters," Mr Elliott said.
"The submission comes after the (Rail, Tram and Bus Union and others) rejected a number of formal requests from transport officials to withdraw the action."
Mr Elliott said the matter was expected to be heard within 48 hours.
In the meantime, the government remained committed to bargaining in good faith but would take all measures to ensure taxpayer assets were not tampered with, he said.
The union plans to leave station gates open as it did last month but this time the Opal readers will also be deactivated, preventing commuters tapping on, rather than giving them an option not to.
Not all stations have gates, although the action will also deactivate stand-alone payment poles at suburban stations.
The Opal system is operated by a private company and Mr Elliott said on Thursday he planned to seek advice on whether the union action would result in the government having to pay any penalties under its contract.
The RTBU is among unions that recently took Sydney Trains and NSW TrainLink to the Fair Work Commission in a bid to keep negotiating a new enterprise agreement and modifications to a fleet of new intercity trains it says is not yet safe to operate.
Premier Dominic Perrottet declared negotiations were over at the end of August, after a month of industrial action disrupting services across several days.
He threatened termination of an enterprise agreement if there was further industrial action.
RTBU NSW secretary Alex Claassens said the government and senior bureaucrats were "the ones responsible for this mess, they can now live with it".