Work will start in the first quarter of 2025 for a seven-year period, with the option for additional contract extensions.
The Enquirer exclusively revealed the win last week after £3bn of track contracts were also awarded by HS2.
The contract will see Costain deliver the design, supply, manufacture, installation, testing and commissioning of HS2’s Tunnel and Lineside M&E systems during construction.
Alex Vaughan, CEO of Costain, said: “Costain has a long-standing involvement with the UK’s largest strategic infrastructure programme and this new contract is a testament to the strength of our collaborative and successful relationship with HS2.
“Our teams will draw on their experience and expertise to deliver world-class systems, using the latest technology to drive efficiency.”