To measure the Citrix XenApp (Presentation Server/Metaframe) or Terminal Services link consumption for an application the best is: publish to users and watch. Yes! Users are totally unpredictable and is very difficult to know every thing that they can do in some scenarios.
But, you always need know how much bandwidth an applications needs to be workable or how many users you can fit in a specific link. To do this you can simulate a user working in your workstation through XenApp or Terminal Services and watch the link traffic in your network card with any link analysis tool that show results in charts. Doing this, you can get some estimate results that can be useful on starter projects.
If you intend give internet access through XenApp or Terminal Services to your users, forget the analysis because anything that you write you will be designated to the near litter available, when an user open a web site with animations or high definition graphs.