It's not a simple thing to detect. Short of broad-scale wiretapping, if I bridge two calls on my office phone nobody will know except my in-house PBX. The tel

It's not a simple thing to detect. Short of broad-scale wiretapping, if I bridge two calls on my office phone nobody will know except my in-house PBX. The telco sees two simultaneous calls into my PBX, but unless they are actively listening in on both lines, they can only guess whether these two callers are also talking to each other.