I'm using empathy for the first few weeks now on Ubuntu 12.10.
I can't find any symbols indicating a contact has the ability to do a video chat or voice chat...
Though I can see a "Mobile" symbol which say "Online from a mobile or Phone device".
PS: I can see a video call, Audio call option enables when I right click on a particular contact.
I don't see any option to configure anything like that.
OS : Ubuntu 12.10
Gnome 3.6.1 (PPA)
Empathy : 126.96.36.199