It's probably also illegal to retaliate against someone for what they said to their union representative and would certainly be compounded by the illegal wiretapping, so we're back to where we started.

Assuming that workplaces operate like a police state is a terrible place to start from and fostering that kind of attitude leads to it's acceptance. I certainly don't hide what I'm doing at work but neither do I expect to have my secure communications intercepted. There is mutual trust on both sides and I see no reason why this can't be the same across the board if the law is there to provide the framework.