We run a multi-campus college, (so 2 x Sites).  On each site we have IT Support, so far, no problem.  But we also have non-IT groups that, in the past, we have enabled to use the same helpdesk system IT uses.  

For example, as well as 'IT Services' we have a 'Facilities and Grounds' department that have 2 dedicated 'technicians', and a 'Catering' department that has another 2 x technicians, so any requester can create a ticket for 'IT Support', or 'Grounds', or 'Catering'.  Technicians should never be able to see requests from the other groups, only the group that are associated with.

Essentially I want each 'group' to exist in their own bubble .. when requesters create a ticket, I want them to select which 'group' the ticket is for, so only those technicians see it.

My question is how would you set this up?  At what layer do I setup these separate 'groups'?  Is it Categories, or Groups, Support Groups?  Do I use business rules to trigger the allocation of the tickets?

I'm open to any ideas.

Much thanks.