This is the first I've heard of people tampering with the brake systems - it's incredibly malicious. I understand some people might be frustrated by the scooters, but is manslaughter really the right way to go about it?
It is all but impossible to get injured due to this vandalism. If the brake cables are cut, you will be unable to even mount the scooter. It's the same UX as on a bicycle: The rider must (unconsciously) press the brake lever to keep the bike in place while getting on it. You'll know right away if the cable is cut--before you even start your ride.
I don't think thats how most people mount a bicycle. You can easily get on it without touching the brakes. After all while you are still touching the ground you are breaking it.