I agree it is rare - the UCI measures seem very effective.

I'm not so sure about the math though, it is trivial for a motor+battery to exceed the 6-7 W/Kg sustained that a human can achieve, thus raising the total system W/Kg.

Also consider that the lightest bikes are 5.5kg or so, and UCI has a minimum weight of 6.8 kg which gives "free weight" for these theoretical cheaters to use...