The contract was awarded through Signalling Solutions, which became part of Alstom on April 1 following the sale of Balfour Beatty's 50% stake in the business in May 2015.
Alstom will supply its Smartlock 400 computer interlocking for the project, which will support the rollout of ETCS on the GWML. Installation is due to be completed by the end of next year.
NR has also awarded Amey an £11m contract to replace power supplies on the London - Reading line.
In 2013 NR awarded Signalling Solutions a £140m contract to resignal sections of the GWML in the Oxford, Swindon, and Bristol areas. Signalling Solutions has also installed Smartlock 400 on the slow lines between Paddington and West Drayton as part of the Crossrail project.
