XFIRE-358 explains that because XFire does not support RPC-Encoding it cannot be used as a client to the Google Web Service.
It also can't be used as a server to a PHP client, because PHP 5's SOAP extension requires RPC-Encoding.
The FAQ (http://docs.codehaus.org/display/XFIRE/FAQ) says,
"However, the basic framework to support RPC/Encoded services is in place. Someone just needs to finish it."