To answer an incoming page calls, the Polycom phone's firmware must support SIP header that indicates that the call is to be automatically answered. By default, UCx sends for page/intercom calls the following SIP header to Polycom phones:
[pre]Alert-Info: info=Auto Answer
[/pre]Based on info from various online sources, some Polycom phones might require a different header - for example Alert-Info: Ring Answer. You'd have to find out what SIP header your phones' firmware requires to answer calls automatically...