Microsoft doesn't want to lost start for WebVR. They announced that WebVR development for Edge has begun. Many hardware companies have launched Virtual Reality Headset. Its mean that VR become good prospect on future. You can watch the development project progress of WebVR at Microsoft's Edge developer website.
Only Mozilla Firefox that already released WebVR to their user. Other browser such Google Chrome, Opera and Edge still under development. Sorry for Safari and Internet Explorer, they not supported by WebVR. So every user can watch VR on their respective browser, in mobile or desktop platform.
For WebVR on Edge, Microsoft didn't said that WebVR will be working on Windows 10 Mobile yet. But surely its will happen because mobile apps or smartphones are has alot Virtual Reality content. So Windows phone user we love that WebVR feature.
Microsoft said that they will be working with other company such Google, Oculus, Mozilla and other that also develop Virtual Reality hardware and software. They will share the details of development progress of WebVR.