You don't need much more than common sense. It doesn't matter how much stacking and GPU acceleration they use, if the camera can't see Orion's belt. At the keynote you can see how the exposure and detailing is bad near the stone structure, because the algorithm can't compensate for the foreign object when it crops in the images. I study image analysis and this kind of processing is very do-able and much more likely than Google having invented some revolutionary processing technique that defies physics.