You gotta get the terms right first.
Most services are running trunked radio systems, most of those are digital, and some are encrypted. You can, with the right scanner, listen to trunked and digital signals. There are no commercially available scanners to listen in on encrypted signals and it would be illegal to do so.
The trunking schemes are proprietary and the radio users like police and fire agencies pay a license (like the license you have to use your copy of Windows operating system or Apple OS) to use them, and you will likewise pay a license fee to the patent owner when you buy the scanner. A base model scanner is pretty inexpensive, the price goes way up if you need a scanner than can follow a trunked system, most of that is for the license.
As mentioned, find out what the agencies are using where you live before you spend the money. scannermaster.com has some deals.