To be speicific, to access shared quetsions, the borrower needs the moodle/question:useall (or usemine) capability in the question bank activity.
Something we talked about, but have not implemented yet, was to change the default permissions so that non-editing teachers get that capability by default. We should probably actually do that.
However, default capabilities normally only apply to new Moodle installs. The normal policy is to not mess with the roles setup when a Moodle site is upgraded. (Does anyone think there is a strong argument for breaking that rule here?) In any case, we should ensure this is covered in the release notes.
Anyway, if you set it up so non-editing teacher has moodle/question:useall permission, then you can let people reuse your questoins just be giving them non-editing teacher role in the shared question bank, or in the course containing the shared question bank. Naturally, they need teacher role in the place where the quiz is, to be able to add questions to it.