The standard applies to traction fixed installations, rolling stock, and auxiliary devices across a wide range of systems: Both passenger and freight lines.
Accessing official IEC standards for free is generally not possible because they are copyrighted and sold to fund the standardization process. However, you can access the standard through several authoritative platforms: iec 60850 pdf free download link
This includes tramways, light rail, trolleybuses, and underground/elevated railways. and underground/elevated railways.