You would have better success in posting this to the LoadRunner group, but....
There are two ways to load test Citrix. Method one involves virtual users operating at the application level of the OSI model. GUI virtual users are staged on Citrix boxes, operating Citirix clients creating load on another Citrix box under load.
The second method involves the direct use of the ICA Protocol for recording, parameterization, manipulation and playback to generate load. The second method is newer. The first method has been around as a possibility since the late 1990's.
If you choose method one, then you need a bunch of GUI virtual user licenses. If you elect to use method two, then you will need a license for the ICA protocol client. If you are evaluating LoadRunner, Mercury (or your Mercury VAR) should provide you with the appropriate protocol/virtual user type for your Proof of Concept (POC) depending upon the method of producing load you elect to make use of.