Yes, we can communicate with ONE space shuttle in orbit. We can communicate with aircraft in the air all over the country, and yes, the BNSF dispatcher in Chicago can communicate with his trains 400 miles down the track.
NO, we cannot however communicate with one hundred thousand space shuttles in low earth orbit, lunar orbit, L5, in transit to Mars, and on the tarmac at Kennedy all at the same time with one system (TRDRS still doesn't work well after 25 years)
We cannot communicate with an aircraft on the ground in Dallas from New York Center traffic control unless the ATC just happens to know the pilot’s cellphone number.
UP dispatchers in Omaha have no way of communicating to a BART train motorman in in the Bay Area.
Unfortunately, what most people forgot when they use the cell phone system as their example is that the cell phone tower system has been evolving with the sole idea of inter-system communications for over 40 years and with an investment of several hundred BILLION dollars (more likely even into the trillions of dollars)
The problem with "one size fits all" solutions, is that eventually, you are going to run into the 400 pound fat lady standing next to Twiggy. "They just ain't going to be able to wear each other’s tube top...." One single radio system solution for all departments/agencies simply cannot work. What would work is to let Bertha buy her own clothes and let Twiggy buy her own clothes, but be sure the two of them talk before going shopping so that they don't buy clashing colors.....
Some areas have done this and their interop systems actually work. Others, like NYC, have not and we see what results. NYC's biggest problem is the "This is my castle, and I don't have to ask anyone’s opinion on what color I paint it," attitude between agencies. Port Authority doesn't want to play nice with Fire. Fire doesn't want to play nice with Emergency Management. The Feds don't want to play nice with anybody....
Here's where the politicos can actually do some good. WITHOUT allowing the individual agencies to have over-ride, appoint a panel of non-radio industry, non-management people (read that field personnel) whose sole responsibility and authority is to decide how these disparate groups can talk to each other without having to have a signed permission slip in triplicate from the agency head. Accept that panel’s report without making changes to benefit the ex-brother-in-law’s radio business, and then implement it along-side the current systems. [/soap-box mode=off]