Re: setting up tikiwiki accross departments
Hi Rob, and welcome to the Tiki Community!
Short Answer: yes to all
See: Perspectives and Permissions if you want to set up the three departments in the same tiki instance. You miight end up using category permissions in the loong run, when you master tiki, but it's not recommended when you are new to tiki.
If qilling to use one tiki instance per dept, see then Multitiki.
There are other options still, but these ones should be enough to get you started.
Cheers