@Uselessbass, the feeds are almost certainly not hosted by the local department that you are listening to. The misconception that Police/Fire/EMS/DPW are employees of the public is false. They are employees of a public company, the municipality that they work in (known as Geographical Area of Employment). Not the general public that lives there. Yes, local governments are public corporations; and yes, taxes pay for their services, but I'll guarantee that their paychecks aren't footnoted "This note was provided by John Q. D-bag who PAYS YOUR SALARY, MISTER!"
If a department is using an analog and unencrypted signal, anyone with a standard scanner or receiver that can find that frequency can listen in; digital public safety channels are newer, more secure, and more expensive to put in place and the handheld radios are usually $5,000+ each, so it's just more cost effective to use the older technologies.
As far as Internet streams of these transmissions, alot of states not only frown upon listening in, but it can aggravate a minor offense into a crime, if not be a crime on its own. In NY, just listening to a public safety broadcast while in a vehicle is a Misdemeanor.
The reason behind 10- and other codes is twofold. First, there are alot of people using one channel to communicate. Codes and other shortcuts to communication keeps the message succinct and standard so everyone can use the air and understand easily. Second, the information is sometimes sensitive, and even before HIPAA (Health Insurance Portability and Accountability Act) of 1996 giving out private information about an individual where it shouldn't be (radio waves, elevators, cafeterias) was kept to a minimum. Remember those signs in hospitals that said "Please don't discuss patient information in public areas"?
So take my information for what it is, information. I'm not condemning listening to public safety transmissions... but using it wrongly could come back to haunt you. Your phone has it's own static IP, MAC address, cellular identifier, and phone number that is all logged. It doesn't take a search warrant to get this information, just a phone call from a police department and a reasonable cause to obtain that information. Phone companies are always cooperative to give this information, because of the terms of service you agreed to when you activated your shiny new toy.