How do I connect to a Thin Client that is connection to a Terminal Server?

I would like to connect to Thin Clients and either view what the user is doing, or be able to take control of the desktop without kicking the user off. Normally this could be done just by using something like RealVNC. The issue is the Thin Clients are connecting to a terminal server, so they all have the same IP address as the TS making VNC useless. Is there anyway to have the same functions that VNC would have (such as the viewer and controller without prompting the user to allow) with the way that the Thin Clients are set up?