The redundancy of the S92 de-ice extends to all principal components. The sensors which detect the ice, the computer controllers (as steve_oc says), and the electric power supply. There are two independant busses, and each large generator is able to hold up the de-ice load after the other fails.
Also, the aircraft was shown to be able to maintain safe flight control after many minutes with it all turned off, as a last resort. I believe it was at least 15 minutes.
Airplanes have simplex systems based on exposure time, since the climb and descend quickly thru the icing region of the sky, while helos flog through it.
I am not sure if the 225 will have a de-ice system, I do recall Helicomparitor telling us why de-ice was not necessary, back when the French were not planning to install it. I think I heard that the 225 was now installing such a kit, as part of its need to meet the market that has been redefined.