I've never been raided, yet!
I have read that very often when a raid is about to take place cell phones in the neighborhood stop working.
Very often at least around here you can observe cops talking on their cell phones while driving. If you have a scanner running you soon learn that anything they want to remain confidential they discuss on their cells. Maybe that is why they want to have exclusive access to such devices,
It's evident to see where such a device might be useful in the other camp.
So, a question might be, "is it illegal to own one, or just to use one? "