Discussions I've heard are not necessarily about someone breaking the law having access to agency traffic. The concerns I've heard are more about scene security and controlling the release of information.
I've participated in numerous discussions with various agencies regarding encryption. Yeah, the streaming audio gets mentioned, but for the most part, I've noticed, it's merely fuel to add to the fire, not the original source of concern.
The source of the concern is things like in the "Dorner incident" in Southern California, where there was both suspicion he was listening, and suspicion he had "helpers" listening. Things like drug cartels and street gangs who are downloading apps and buying scanners and listening. And things like various intelligence sources indicating that radical extremist groups are constantly probing our vulnerabilities for the next 9/11 level attack, and day to day police operations are a target to be exploited.
I could tell some hairy stories where encryption would have saved the day, but NDA's and professional courtesy demand I keep my yap shut. For now. I've had direct involvement in several VERY high profile events where unsecured communications played a negative roll in the final outcome.
The bottom line for everyone is, there is a variety of reasons that encryption is gaining on us. Not all of them involve streaming. Some of the threats are real, some are "perceived". But perceived threats are just as real, to the decision makers. You won't talk them out of it.
These systems aren't intended for the general population's consumption, and frankly, the decision makers really don't care one way or the other about hobbyists.