I see no humor here at all. I have kept CBS with cleaner shrimp and peppermint shrimp w/o any problems... that's not to say there will not be problems with mixing them. After a while I got paranoid and banned the CBS to the refuge just so there would be no issues.
IMO CBS have three "motives" when it comes to other shrimp. 1. If food is light they eliminate competition. 2. If they get hungry enough they will become predators and search for food. 3. If room and/or food is not an issue there is no reason to risk harm in fighting/killing other shrimp. All that said, they can and will kill other shrimp if they want to.
As far as not seeing them... I had about 6 peppermint shrimp and three cleaners in my 110g. I hadn't seen the the peppermints sense the day I put them in, even with plenty of night time viewing. They were all very small so I assumed they became a snack for my 6-line I assumed they were dead. A couple weekends ago when I tore down the 110g I found all 6, all of them grew substantially from when I got them. Now I have around 20+- peppermint shrimp in my 55g and rarely see any of them, when I do it is at night while viewing the tank with a red light.