I have had my CBS in with about 4 different types of shrimp (sexy, cleaner, fire, harlequin) and never once did he bother any of them. The CBS is the oldest creature in the tank about 5 years and the most I have ever seen him do is raise his claws at the clowns if they get to close.
They tend to hold there own, but IMO I don't think they will go out of there way to kill another shrimp. Maybe I am lucky but thats what I have seen with mine.