After a lot of digging it looks as though this cannot be acomplished. It appears as if you can't even set the Auto_Answer option in the config file to get the phone to at lease answer automatically in speakerphone mode.

I did find someones script that essentially create a telnet session to replicate button presses, but as our phone are in remote locations managed via the Internet, we have telnet closed and so this will not work for us.

Shame.