One of the train's two locomotives left the rails last Sunday night when the train hit rocks that had fallen in a "definitely weather-related" incident.
Two of the train's three carriages also left the track but had remained upright.
Dunedin Railways chief executive officer Craig Osborne said there were challenges in moving a locomotive and two 25-tonne carriages back on to the rails, but the main priority had been "making the job safe".
A "good partnership" had been built between his staff, KiwiRail and external contractors.
Some further rail repair work in the area would have to be undertaken, and it was hoped the Taieri Gorge service could be resumed early to mid next week.
Convener of a planned Dunedin South Lions Taieri Gorge annual rail walk Allan Hamilton said 300 people had booked to take part on the two-hour charity fund-raising walk on part of the Taieri Gorge line this Sunday, but the walk had been rescheduled for May 26.
