The single headline advantage of Sony's EXMOR tecnnology is its Column parallel analog-digital conversion, which I believe helps greatly because the majority of sensor read noise in other designs enters during the fast transportation of the analog signal along the edge of the sensor and then to tue ADC, not in the photosites themselves. So digitizing before that step helps a lot. This approach also sems to make high frame rates easier to achieve, so is good for hogh resolution video.
The good news is that this technique is not a Sony exclusive, even though Sony has so far made the most of it in the world of larger sensors for "dedicated stills cameras".The same method was used first by Samsung, but in a video camera sensor, and it seems that video sensors have been the main area of application so far.
So my guess is that Canon is working on something similar --- unless it already has a different and even better idea in development. By the way, it also seems quite possible that some other sensors from other designers are also using column-parallel ADC, without talking about it so much (perhaps because it would sound rather "me too"). Some candidates are the sensors for Nikon One cameras, the video oriented multi-aspect ratio sensors of the Panasonic GH1 and GH2, and the sensor of unstated origins in the new Olympus OM-D E-M5. Panasonic has said that the GH1 and GH2 sensors produce digital output (as with EXMOR) whereas its other 4/3" sensor produce an analog output signal for off-board ADCs (as with Canon) and that those sensors are significantly more expensive to make than its other 4/3” sensors, which is why they are not used in all recent micro four thirds bodies. So maybe Panasonic is part-way there, but the new approach has problems with low yields, pushing the price up. And maybe Nikon and its sensor partners are also about the EXMOR monopoly, or already have.
P. S. it is often stated as obvious fact that the D800 sensor is from Sony, sometimes supported by the fact that Nikon does not have sensor fabrication equipment. However, AFAIK, neither Nikon nor Sony has said this, and the possibility remains that Nikon has been involved in the design of this sensor (perhaps in partnership with Sony, or Aptina, or one of the other good sensor designers that have been working mostly with smaller sensors up till now, such as Toshiba). Fabrication can be contracted out to one of several competent fabs, so Nikon's lack of a sensor fab. is irrelevant. For example, Aptina is a fabless sensor designer.
Added: talking of Aptina (likely sensor supplier for Nikon One), it is about to release an APS-C sized sensor for "DSLR/mirrorless", which does 14-bit ADC on the camera chip itself, and offers 10 fps, 1080p30 video etc.:http://www.aptina.com/products/image_sensors/mt9h004/
I have no idea how good it is or if any major camera maker will adopt it, but the competition seems to be getting stronger, and the idea that a camera maker is always better off doing all its own sensor design in-house rather than making use of the technologies offered in a competitive market place of companies that specialize in sensor design makes less sense than ever to me. Frankly, the all in-house philosophy verges on "log cabin in the mountains off the grid survivalism".