Not only can you play SteamVR games on Windows Mixed Reality, you can also play Rift games, thanks to Revive.
SteamVR integration with Windows Mixed Reality (WMR) is a big step in the right direction for the emerging VR platform, but it doesn't mean you're stuck playing only games available from Steam (or, of course, the Microsoft Store).
LibreVR's Revive is a tool that effectively reroutes Rift games downloaded through the Oculus app over to the SteamVR platform. It was originally intended to work with the HTC Vive, but you can get it all working with Windows Mixed Reality.
Full story from the WindowsCentral blog...