Hi Stephen
I tried using the default non editing trainer role in a quiz and this allowed the viewing of questions from the system category in the quiz.
This role doesn't have many permissions - probably the View server repository and View file system repository need allowing
I tried to add a question from the question bank based on a tag in a question but couldn't see an option to search by tag. This is also the same for random question so don't think his has been implemented yet.
regards