The £11.6m deal covers a series of associated works to support the electrification of roughly 74km of railway, which is set to be conducted under a £160m investment programme by the Scottish Government.
The route connects Edinburgh and Glasgow and is expected to become electrified by March 2019.
Scotland Transport Minister Humza Yousaf said: “The Scottish Government’s funding of the Shotts Line electrification, and our overall £5bn package of investment in our railway, demonstrates our ongoing commitment to improving the Scottish rail network.
“This work contributes to the transformation of services across the central belt as part of the wider package of investment to enhance rail travel between the country’s two biggest cities, meaning passengers will see shorter journey times, increased capacity and better reliability.”
The deal will see Carillion Powerlines carry out platform reconstructions and provide necessary enhancements to nine stations on the network, including the installation of lighting, CCTV and customer information systems.
In addition, Livingston South and Breich stations will be completely re-constructed, with platforms extended at Carfin, Shotts and West Calder in order to allow longer trains to operate along the line.
All works are expected to be completed in the second half of next year.
Network Rail route delivery director Iain McFarlane said: “This contract is another step forward for the delivery of the Shotts electrification project and further underlines our commitment to investing in and enhancing our infrastructure as part of our UK-wide railway upgrade plan.
“Electrification of the line across North Lanarkshire and West Lothian, coupled with improvements at stations, will transform the journey experience for rail passengers who will enjoy the benefits of improved services for many years to come.”
The electrification of the line is also anticipated to enable the introduction of the new Hitachi Class 385 rolling stock onto the line.