WSPS, need about 35-40 knots (varies somewhat with weight of ac) to cut a 3/8" (10MM) Steel cable. In most cases WSPS only protects people who are doing things against company policy to begin with. Cruising 50-100'AGL, canyon runs etc.
The exception there would be powerline patrol, mustering, fish and game surveys, etc, military etc.
Crab, it all depends on where it his the aircraft. many of the time the wite hits the rotor, or comes right through the bubbe, others it catches the skid gear and inverts the aircraft.
The last Transmission Line Construction project I was on was built using 50kp hardware thats 50,000lb. or 22,680kg break strength. That would take down a C-130 without batting an eye.... By the way, that happend too.