Note that there is also an encrypted version of this system that's not publicly accessible. I'm not sure about the quality of the encryption used, but I do know that police traffic and ambulance traffic often goes via encrypted channels.
I'm also not sure if this is a system that's legally protected or that the government simply hasn't bothered trying to take these sites down.
That's called C2000 yes but it's mainly for voice. It can handle text messages too. It's based on Tetra. And it's two-way. Indeed very well encrypted.
P2000 is one way and based on FLEX, a paging protocol. It's indeed only used for fire and ambulance. The police data is too sensitive so they use C2000. Though you will see police traffic related to accidents etc.
But no P2000 isn't protected and the government even used that website themselves :) Not officially though, I guess.
I think this is also because most fire departments use a lot of volunteers which makes their activities a lot more public.
Not only is it legal but many police forces around the country use this site to keep an eye on the traffic. At least they did more than a decade ago.