Hi,
No, only one Citrix license gets used per concurrent login. A user cannot be logged into the same Citrix session or server Farm by using their same login credentials. If they did then they would just reconnect to their existing session. As far as terminal services goes. This is just an honor system thing that MS has setup. TS licensing, IMO is pointless. I have installed the 120 day grace license on a TS / Citrix server once and it NEVER timed out. I eventually purchased a 5 pack to stay compliant. You can look at the certificates that are being issued and if you can make sense of them then I think that you would be the first. So, in order to be compliant with MS, you should have just as many TS licenses as you have concurrent users. The same goes for Citrix, however Citrix will lock you out if all of your sessions are being use.
HTH