More than 200 Carillion jobs under threat after its collapse last week have been saved.
Construction group Kier and French civil engineering firm Eiffage were awarded a £1.4 billion contract last July as a joint venture with Carillion to build tunnels on the first phase of the HS2 rail line between Birmingham and London.
Kier and Eiffage have now taken a 50/50 partnership to build the tunnels from North Portal Chiltern Tunnels to Brackley and Brackley to Long Itchington Wood Green Tunnel South.
As a result, 51 Carillion employees, including apprentices, have been offered the opportunity to join Kier/Eiffage joint venture, with continuous service being maintained.
In a separate announcement, Kier has assumed full responsibility for the smart motorway schemes it had been working on with Carillion for Highways England.
All employees currently working on the projects have been offered the opportunity to join Kier with around 150 employees making the transition in the next week, including seven apprentices.
Wolverhampton-based construction and infrastructure group Carillion was placed into compulsory liquidation last Monday after struggling with £900 million of debt and a £590 million deficit.
The company was leading the development of One Chamberlain Square, the first building on the £700 million Paradise scheme in Birmingham city centre, and the £558 million Midland Metropolitan Hospital.
Kier's chief executive Haydn Mursell said: "We have been working collaboratively with our clients and are pleased to have reached agreement with government.
"We have been able to take action quickly and reassure the project teams that they continue to play an important role in the delivery of these contracts."
Transport Secretary Chris Grayling added: "This announcement demonstrates the strength and purpose of the joint venture contracts agreed on HS2 works and the smart motorways programme.
"These have enabled Kier and Eiffage to step in as planned and guarantee continued employment, apprenticeships and the seamless delivery of these vital projects.
"HS2 and Highways England carried out, at the point of award, additional due diligence to ensure, even without Carillion, these projects would continue.
"Both Highways England and HS2 will continue to monitor the situation."
HS2's chief executive Mark Thurston added: "We welcome this decision by the remaining joint venture partners.
"Through this difficult time, the team has continued to deliver and we're grateful for their ongoing hard work and dedication.
"No time delays or costs implication have come about as a result of the events of this week, underlining the strength of the joint venture approach taken by HS2 in procuring its partners."
