I couldn't get that embedded video to work, but here's the original on YouTube.
View: http://www.youtube.com/watch?v=8Nd13ARuvVE
The Cancellara footage and argument is quite convincing when you see the slowed-down sections, especially for the second race. It's the combination of acceleration without significant apparent change in effort with the wierd hand movements. The noise of the motor would not be able to be heard over the motorbikes and the crowds - and I notice that the accelerations both occured on very noisy sections.
Although it is still not much more than speculation, I am starting to get a bad feeling about this.