I am also curious about why the concern for privacy in the first place.
And no other reason than; because we should be able to. The constitution really is law, and the spirit of that law is that we are free to conduct our lives as we see fit without suspicion of malice. You wouldn't tolerate the ability of strangers or of 'designated enforcement authorities' to peer over your shoulder or listen to every word you spoke in real world conversations, so I'm not sure why anyone would be content to tolerate it in electronic communications. I guess the ability of monitors to be "there" without really being physically present is pretty disarming to most folks.
You do know that the courts have consistently held that there is no implied privacy while transmitting on the public airwaves, right?
The short and simple answer to your question in the thread title is NO.
The radios spectrum is a public resource. It is also public in that all activities carried out there such as transmitting, are done publicly. Transmitting in the radio spectrum is a PUBLIC act. Privacy is not a reasonable expectation for the party doing the transmitting to have in the first place and there is no implied privacy. Radio listeners are not being nosey. It is the people who do the transmitting that are being exhibitionists in public. Common sense suggests that privacy of radio communications is best safeguarded by the party doing the transmitting. IIRC, it's also written in Part 90 that the responsibility for securing privacy of communications is on the party that does the transmitting. That's where the use of encryption then comes into play.
We technically DO NOT have a constitutional right to transmit on the public airwaves. This has been upheld by the FCC and the courts in many cases involving pirate radio broadcasting. Pirate broadcasters often believe they have a constitutional right to transmit on the public airwaves, but they don't. Transmitting on the air is a privilege, not a right. The Constitution is not at issue here.
When I transmit on the public airwaves for ANY reason, including on my cell phone, I don't expect privacy at all since actual privacy does not exist, there is none implied, and it is not reasonable to expect any either. I fully expect my radio transmissions may be overheard by somebody out there and without my knowledge or consent. The lack of any implied privacy goes with the territory while committing a public act in a public place. I welcome them to listen all they want to and to their heart's content. The airwaves are public and the world has ears.
While the Motorola 900MHz DTR and DLR radios are technically not encrypted, they are completely scanner proof due to the nature of FHSS and their digital (VSELP) operation. Even if the FHSS operation were stopped and stayed on a single frequency in the hopset of 50 frequencies, the occupied bandwidth of the 8-level digital modulation scheme used is wider than what a narrowband receiver will accept. And then you would still need to decode the VSELP digital. Aside from Motorola and 3-letter government agencies, the only inexpensive and practical way to monitor the DTR and DLR radios is to have one yourself, AND it has to be programmed to the same frequency hopset and talkgroup ID being used. Private 1 to 1 calling is not monitorable by another DTR or DLR radio not part of the 1 to 1 call.
I actually have had a case where someone who knew what they were doing tried to listen to my wife and I when we were using our DTR radios at a ham flea market. He failed of course. This was at NEAR-fest at the fairgrounds in Deerfield NH. My wife had gone to get food from one of the food vendors while I was still wandering around the fairgrounds. We were chitchatting on the DTRs to figure out where to meet up when a guy a table asked her what frequency we were using. Since she didn't know, she asked me over the DTR radio and said a guy at a table was asking her. I replied that they are FHSS digital radios operating in the 902-928MHz ISM band. The guy then said to her "Oh! So THAT'S why I can't find you on my spectrum analyzer!!" LOL. He was expecting to see a strong narrowband emission pop up somewhere in the UHF part of the spectrum and remain there for the duration of each transmission. We were hiding in plain site with who knows how many other FHSS devices operating in the 902-928MHz band. We were also using a Private talkgroup programmed in our DTR radios so they are not monitorable by other DTR and DLR radios in the area.
I challenge anyone to try to monitor private 1 to 1 calling on my DTR radios "on the fly" to demonstrate how "un-secure" they are. All I ask is they show me how they did it so I can do the same to monitor other DTR and DLR radios. Listening to the available public talkgroups doesn't count since anyone with a DTR or DLR radio can do that.
The bottom line is if you want communications privacy, you have no business making an electromagnetic emission. IOW, stay out the radio spectrum.