Hey, you NEED a LCS sensor track on your layout. Regardless of the size of your layout. you only need one sensor track. One might think you also need fast track to use the sensor track. This is not quite true. Lionel was marketing a kit to adapt other kinds of track or convert them into a sensor track.
Why you need one: Lionel quit distributing engine information on the orange modules you used to load into your CAB 2 base and computer for the Lionel Utility on your PC application. Now the trains have an I/R element on their underside that is read by the sensor track. There is no other easy method to get newer engine information into your CAB 2 or CAB 3 system. A sensor track makes this a breeze. One pass of the engine, or Lionel dining cars with talk etc. in them and "bingo" the information is captured to the base 2, and your IPhone running the LCS app. The couple of cabooses with crew talk in them might have this element in their underside as well. I'll have to unbox one and check.
So yes, the newer cabin car cabooses (part # example: 2326770) have the active element on their underside to transfer information to the sensor track. Again the sensor track IS THE ONLY WAY to read the car's important information!!!!!!! One sensor track per layout - very necessary and valuable!
Subsequently, you can transfer the engine information from your smart phone to the CAB 3 base. I don't think the BASE 3 will directly read the orange engine modules. At least I have not found out how yet. A fellow named Shawn's Trains is perhaps the best board resource for learning things about the Base 3. He has a 3 part tutorial that is excellent, and very professional in its production. His tutorials are found on You Tube. Somewhere in the long string on the CAB 3 is a link to them. That topic has grown so lengthy, so maybe you can use the search tool to find Shawn's multiple posts to that thread.
So, yes, obtain the sensor track! Everybody running newer and current issue Lionel engine and certain rolling stock needs one! (If you want intelligent control of your piece)