For years the plan has been to bulldoze most of the history-steeped buildings and build a large housing development and community facilities on the site, which is owned by St Modwen property developers.
Gemini Rail Services, which has been using the main buildings in the meantime, were going to be housing in a new onsite building.
But the firm has now announced plans for expansion - using the existing Wolverton Works buildings
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Local rail expert Phillip Webb said: " It is said that Gemini rail is finally making a profit in nearly a decade. they are going to be working on a new traction propulsion package and well as refurbishing the interior of 18 SWR's class 442 fleet."
He added: "Gemini is also going to be extending the historic 200-meter-long lifting shed to accommodate 10 car class 720s. It's likely two new bays will be fitted with 4 elevated tracks to create a new modern maintenance facility.
"Even though this is a win, the fight still goes on to save the historic sawmill and smithy shed east. But it's safe to say the historic site lives on."
St Modwen still has outline planning permission to build 375 new homes on the land surrounding the site. They also plans a community building and employment space.
A spokesman said: "The regeneration of Wolverton Works will support hundreds of current and future rail-related jobs for the town. It will also deliver much-needed new homes and community facilities for Wolverton."