Tresspassers are Trespassers
If if they detect something "unused" and say they will go away if someone else wants to (lawfully) use the space. No, this silly idea just won't work. The whitespace bozos need to go to 2.4 GHz where they belong.
If they don't accept the part 15 (FCC) rules of non-interference they are bad. Of course, if their technology was so good, why not hide out in some police dispatch frequency when it isn't being used? Besides, if two devices decide upon different places to hide out, how will they find each other? No, it won't fly, and sugar coating it with some lobbying effort won't make it any better.