It doesn't for me. Microsoft said during their WP8 launch event that Skype would run in the background so you don't have to have the app open to receive a video call. I tried doing just that, and it didn't work! What gives?!
Works for me, whenever someone calls I receive it as if it were a normal phone call, just like the Gwen Stefani 8X commercial.
How are you getting it to work?