In December, it narrowly escaped the wrath of the Gospers Mountain mega fire and today the first engine in more than eight years arrived at the platform.

Zig Zag Railway chairman Ben Lawrence said the locomotive was being used to test the tracks after a restoration and repair project of the entire line had been completed.

"Today is an exciting day for Zig Zag Railway, one we have been waiting for, for eight long years," Mr Lawrence said.

"The Gospers Mountain fire caused significant damage to the railway in December 2019.

"Many people saw the images of the infrastructure we lost, however the tracks themselves were also impacted, with sleepers in some sections burnt out and three significant buckles in the track created due to the intense heat on the fire ground.

"Ageing infrastructure and damage from intense storms and vandalism was also evident along the tracks, all of which needed to be fixed before we could even look at a return to service."

Zig Zag Railway recently engaged a specialised rail infrastructure company, Onrail Industries, to assess the full seven kilometres of track and complete a repair and restoration project.

"Thanks to the volunteers and the Onrail Industries team, we can finally bring a heavy engine, the first since 2012, all the way from the Bottom Points Depot to Clarence Station - it's a moment we have been working to for a very long time," Mr Lawrence said.

"The repair and restoration process included the replacement of 2,000 sleepers, 500 tonnes of new ballast, 6,000 dog spikes and 3,000 shoulder plates.

"We also undertook a 'Top and line' process by which we check that the line is straight where its meant to be straight, curved where its meant to be curved and any dips and bumps are flattened out so that we can ensure a smooth trip for our visitors when we can return.

"You could say, it's as good as new."

Zig Zag Railway Operations Manager Thomas Worley said that over the past nine years in particular they have put so much work in as a volunteer workforce to get to this point.

"It's just fantastic to be up here and celebrating this achievement," he said.

"I went for a test run and the track is so good, it is so smooth at the moment and it is in the best condition its ever been in at my time at the railway over the past 15 years I've been volunteering."

Mr Worley said that 2020 looked promising for having a steam locomotive arrive at Zig Zag Railway.

"We are certainly hoping the steam locomotive will arrive very shortly and then a train which will be even better," he said.

"The steam locomotive will be a key milestone in returning to passenger operations."

Mr Lawrence said the diesel locomotive, originally from Emu Bay in Tasmania, had also recently been lovingly restored by volunteers.

"Our volunteers have spent more than 1,000 hours making sure this locomotive was in top condition, ready to roll out and assist in the testing of the tracks and the eventual return to services," he said.

"The rebuilding of Zig Zag Railway isn't just about making sure the tracks are ready - we have had to rebuild almost all of our infrastructure, the locomotives and the carriages as well as all of the policies, procedures and training that underpins our operations.

"It's a big job, but we are excited to have reached this stage."

No date has been set for the return to passenger services.

Zig Zag Railway would like to acknowledge the assistance of Lithgow City Council, the NSW Government and our industry partners who have assisted in other ways during the bushfire recovery period.