I'm considering storing the URI for a workitem from our TFS environment in our helpdesk system, however looking at the URIs TFS gives us (vstfs:///WorkItemTracking/WorkItem/327), there doesn't appear any recognition of which team project it is associated with, which makes me wonder how meaningful they are?
Is it possible to load a workitem by just URI? Or will I have to store the Project URI as well?
The URI is meaningful since the item number at the end of the URI is unique and links to the item in TFS. I think storing this URI in another system makes sense considering the fact that it contains the identifier of the item.
The work item URI is unique across the Team Foundation Server in TFS 2008/2005 or across the entire Project Collection in TFS 2010 (TFS 2010 has a new notion of project collections - see here for more information). The Team Project that it is in does not affect the ID.
Therefore to have a unique reference to the work item so that you'll always be able to get to it in the future you need a TFS server URI and a Work Item URI (i.e. http://tfsserver%3A8080/ + vstfs:///WorkItemTracking/WorkItem/327)
If you will only ever have a single TFS server or a single TFS project collection in TFS 2010 that your CRM system is attached to then you can assume all work items are linked to a single TFS Url.