There is a special Speaker HSN1000 via adapter cable 0185180U01 and to adjust volume and or turn PL on off you need, GMN6147b microphone with the 3 buttons side buttons. These options are for techs to trouble shoot and test the station, and not typically used the way I think you are describing to be used.
I really think a tone remote setup would be a better solution for you, if station is equipped with tone remote board. This way you could put remotes in different locations through out the station, and also have transmit capabilities.
Another option is to by a public address PA, radioshack sells them and run speakers throughout.