I agree with all aspects of your post. Especially the encryption aspect..cant agrue with that. They are expensive but I was still kinda shocked that they weren't a smartzone system or the like. Here in South Dakota we have a state wide system VHF p25 smartzone system with 50 some sites and only have 800,000 people in our state. With the greater tax base in So Cal I'm hoping they could afford it lol
The difference between South Dakota and southern California from the aspect of radio is about as large as it can be. There are about 5 times the population of all of South Dakota in the City of Los Angeles, just one of 88 cities in L.A. County, which has 10 million people. The continuous urban area that L.A. County is a part of, with Ventura, Orange, Riverside, San Bernardino and San Diego Counties, a megalopolis is what I call it, is 17.5 million people. Mix in the L.A. Airport, one of the busiest seaports in the world, manufacturing, petroleum refining, high rises, heavily visited beaches and amusement parks, the busiest freeway system in the world and the most volatile wildland fire environment in the world; and what you have is an extremely complex RF environment to deal with. Frequency licensing is not easy in this environment.
Just one unit of Cal Fire's 21 operational units, especially in southern California, has far more activity than South Dakota's Wildland Fire Division. Statistics for other agencies in the area are very high and radio systems have to have many more frequencies than less active agencies in rural areas.
Terrain is a factor as well. The mountains surrounding this megalopolis are steep in comparison with what South Dakota has. L.A. County is split by the San Gabriel Mountains, and you don't realize how rugged they are until you try to walk cross country in them, something I've done a few times fighting fire. You can't put up a tower or two in L.A. County and expect to cover much territory.
Then the seismic factor comes in. Communications systems need to be redundant and physical facilities hardened to withstand earthquakes. Not enough work has been done in that area, but quite a bit has been accomplished.
L.A. County is one of the limited number of areas that were granted frequencies in the 470 - 512 MHz range, the so called UHF-T band. The U.S. Congress voted to eliminate land mobile radio use in the band. I can't count how many agencies in southern California have most, and some all, of their frequencies in that band. There has been far more work on interoperability and mutual aid systems using UHF frequencies than you might think. Fire departments with wildland fire incidents in their jurisdictions have VHF-High radios (mobiles and handhelds) as that band is the nearly universal for wildland firefighting. There are fixed and portable patching or cross over systems as well.
The complexity and expense of putting in a regional trunked radio system is mind boggling. Some members of Radio Reference don't believe it can be done. Only time will tell. I think it can be done, but I'm not holding my breath.