TEC is setup in busy areas like los angeles. Under normal IFR flights you usually go from tower control-departure-center-arrival-and then to tower at your destination. With TEC you just stay with departure/approach since its usually a quick hop, never go to a center controller. As far as the routes, they are usually below 10,000 and can be found in the front section of the jepps (never used NOS). Keep in mind that not every region has TEC so you might not find TEC routes in your jepps. I have never filed while using TEC so I cant give you much detail on filing. However, that is the great thing about TEC. You don't have to file, you can just request TEC to your destination with cleareance or ground (makes life great, I love TEC). But watch yourself if you don't file a flight plan and pick up TEC, dont forget to have an alternate if your destination is below mins (i have heard of people getting in trouble that way).