TV gets stolen because they give the 'key' to the public, those who pay. Some of those folks are, oh my, dishonest. They hack the electronics of the receiver box to figure out what keys are needed, HAVING a working key available.
The radio traffic we listen to, only the intended recipients get the key, and they tend to be more honest. Yes, if a legal keyholder gives you a key, and you buy the appropriate radios/equipment, you could program in the key and listen. For about a week, till they change the key again. 'giving' you the key isn't easy, the beat cop doesn't know what it is, it's loaded from a 'trusted' individual or over the air (encrypted itself) rekeying signal.
Bottom line, if it was easy, they wouldn't USE that mode. When digital was a future dream, 'encryption' consisted of 'voice inversion', mostly, and yes, you could listen, with some fairly simple electronics you could build easily. That day is done. It's now on GMRS/FRS handie-talkies you buy in Wal-Mart as 'toys'.
Any 'break' in current codes WILL require hundreds of computers, and days or weeks of time to 'break' a given message. By the time you break the one recorded message you worked on, the key has changed again, start over. And it's no easier the second time.