Currently call manager only advertises audio capabilities for an intercom call so there's no way to make the intercom feature use video.  On the other hand you can setup an auto answer line on someone's phone that can be used like an intercom and if both sides are video capable you'd see video too, but the audio would be two ways as well all the time since the phone auto answers rather than an intercom's one way audio until the intercom line is pressed to speak back.