Transport for NSW and Sydney Trains are in the planning phase for what is being described as a "broad" upgrade of train radio systems, work it says pre-dates an outage of a digital radio system last week.
Disclosure of the project came after ABC News reported details of a confidential document that found parts of the digital train radio system (DTRS) were "obsolete".
The report, from 2022, stated that funding was being reallocated as a priority.
Sydney Trains confirmed to iTnews that "parts of the DTRS system would become obsolete over the next five years", but said the transport operator was aware of that since 2021.
It is understood the network switch that failed last week was not a component of the DTRS that had been flagged for future obsolesence.
"We continuously review the lifecycle management of our systems as part of asset management plans," the spokesperson said.
The spokesperson added that a "broader technology upgrade" plan is being worked on for radio system upgrades, inferring this would include DTRS but could also be much larger in scope.
"Transport for NSW and Sydney Trains are working together on a plan for the broader technology upgrade for train radio systems, while continuing to keep the current system operating reliably," the spokesperson said.
The spokesperson said the next major refresh of the DRTS will happen when 5G technology is more mature.
Last week's DTRS outage meant trains were halted at stations for more than hour in the afternoon, with knock-on effects that stretched well into the evening.
An investigation into the outage is continuing.
