LIMITED freight and diesel passenger service trains will start operating through the Blue Mountains from late January, but the reinstatement of electric trains is yet to be determined.
Areas around the railway lines were extensively damaged by bushfires with some infrastructure destroyed or damaged in the out-of-control blazes that swept through the region.
A Sydney Trains spokesman said crews had been on site inspecting damage.
"Our crews are working hard to construct and commission safe-working systems which would allow limited freight and diesel passenger services to operate between Mount Victoria and Lithgow from late January," he said.
"Due to the extent of the damage, it will take longer to fully rebuild the infrastructure, including overhead power, to run electric trains.
"Buses will continue to replace trains between Mount Victoria and Lithgow in the meantime."
The spokesman said a significant amount of infrastructure was damaged or destroyed.
"[This included] large sections of the communications and signalling systems, and around 50 kilometres of high voltage electrical infrastructure including 100 timber power poles and wires and approximately 300 fire-damaged trees near the railway," he said.
"Burned vegetation and damaged power poles in the corridor need to be inspected and removed before our crews can enter sections of the railway to thoroughly investigate the damage."
In addition to the bushfire damage, some work planned for the Springwood to Lithgow Rail Corridor Modifications Project in December was postponed due to the bushfires and will be re-planned during the months of recovery.
NSW TrainLink will continue to provide regular updates to customers on its website, trip planning apps and our Twitter accounts.