It is not on the CSP system, it is a different system that has a common frequency. Several things have to happen for you to hear it.
The common frequency has to be programmed into your scanner.
The common frequency needs to rotate into the control channel slot in the other system.
The scanner must be using control channel only scanning in search mode OR a common TGID needs to become active.
By deleting or locking out the common channel(s), you can control what you hear much better. There are a couple other threads that has which frequency it is but I believe it is one of the freqs used at an Intellipeater site from Troop L or B.
chris