Update 2019: No IE actually supports WebRTC and no IE ever will. In 5 weeks Microsoft Edge will die and long live Chromium based Edge.
That supports WebRTC.
As of Sept 18 2015 Microsoft Edge (Spartan) is now supporting ORTC. Links and such are below.
BLOGS - http://blogs.windows.com/msedgedev/2015/09/18/ortc-api-is-now-available-in-microsoft-edge/
https://blogs.office.com/2015/09/18/enabling-seamless-communication-experiences-for-the-web-with-skype-skype-for-business-and-microsoft-edge/
http://blogs.skype.com/2015/09/18/skype-for-web-and-skype-for-outlook-com-update/
DEMOS on Edge Test Drive - http://dev.modern.ie/testdrive/demos/ortcdemo/ for Edge-to-Edge video calls
http://dev.modern.ie/testdrive/demos/twilioortc/ for Edge-to-Phone calls by Twilio
http://dev.modern.ie/testdrive/demos/simplewebrtc for Edge-to-Chrome/FF audio calls by &yet
Open Source projects for WebRTC-ORTC interop – from partners working closely with us
https://webrtchacks.com/first-steps-ortc/ - blog post and open source project by &yet
https://www.npmjs.com/package/ortc-adapter - open source project launched by Twilio
Hope this helps. Healy in Tampa