I can pretty confidently say that all bikes with Bosch ABS get their speed from the ABS sensors. We could have new ABS rings with 8% fewer pulses made over 1 revolution, and it would correct the speedo, and ABS would still work perfectly.
This... is an interesting thought.
Some of you may know that I was unable to put a 14T sprocket on my hyper because it would hit the rev limiter in 2nd gear only at 8,000RPM. I wonder if there is a way to fool it with different tone rings.