That System Sensor unit only uses CO to also determine the validity of a fire alarm, not a separate CO signal. They're used in "critical" locations or other areas that are subject to false alarm due to enviroment (theaters, etc.) We've got a bunch of them installed at one of our sites that has somewhere over 60K detectors and modules installed.
The CO1224 doesn't necessarily need a 6 conductor, you can wire continous on a single 4, and then wire the trouble relay/contacts in with the detector circuit. Basically, you wire them NO circuit and the trouble relay in series with the circuit. Most smaller "modern" design panels have a designated CO zone type (alarm on short, trouble open) however if an older doesn't, I've always recommended people to wire it like a fire alarm and program it the same.