Site will be associated to the requester through a Departmnt

So that I understand this correctly;

If I have two sites (A & B) and both have an accounts department, is account department A a separate entity to accounts department B? e.g. we have London and Paris and we need to see the results (in reports and searches) for users from each site rather than combined.

This brings me to a second question; a requester working for Paris accounts transfers to the London office (or changes jobs within Paris). Do the jobs that were originally logged when they worked in Paris accounts now get analysed as the new position or does the job stay as at the point the request was made?

Thanks - Terry