They seem to be quite dedicated to ToF, as they bought not one but two companies (3DV Systems, Canesta) just to have their own inhouse ToF system [1].
I found two images from the inside of Kinect One, if someone is interested: [2] [3], from the Wired article [4]
The processing system on the other hand might be in-house, or probably with the help of their amazing MS Research team. The demo in this video is absolutely state-of-the-art tracking: [5].
