The first question to ask yourself is how separate do you want them to be? Do you just want to separate tickets or do you want to separate Problem incidents and Knowledge Base as well.
If you want to separate tickets, here are some articles and a video that will at least get you started. They won't be the complete solution for your area but they will at least help you know what can be done. Basically, you will need to first route them to the right group, set the correct permissions so only those groups can see them, and then make sure when they get escalated they will go to the correct group.
http://www.screencast.com/users/nmitchelmore/folders/Symantec%20Workflow%20Topics/media/9f328afc-ab7f-4b87-a038-59f26dbc6cef
http://www-secure.symantec.com/connect/articles/service-desk-7-assigning-initial-permissions-incidents-based-location
http://www-secure.symantec.com/connect/articles/auto-escalation-based-location
Another thing I should mention is even if an enduser doesn't have rights to see anybody elses tickets, if they actually search for a specific ticket number they will still be able to see a summary of that ticket. I don't know of a way to avoid this.