Most partyline manufacturers provide some form of compatibility with Clear-Com systems 

Tecpro / ASL all offer products that are compatible with Clear-Com (in terms that they will connect and pass audio). Call signalling and remote mic kill functions may not be compatible across different bands 

Extract from Tecpro manual
CLEARCOM COMPATIBILITY: Tecpro stations are completely compatible with Clearcom stations. A Tecpro stations added to Clearcom will function and visa versa. However, Clearcom stations have a lower bridging impedance and may degrade a Tecpro system slightly due to a reduction in sidetone stability incurred when a Clearcom outstation is used in a Tecpro communications system. Additionally the Tecpro override tone may be reduced in effectiveness by Clearcom stations.