I'm working on a blog that has two users that post and write pages to it. We modified the database so they would each be Level 10 (same level as Admin), enabling them to write/edit/delete at will without having to e-mail the admin to do so.
When one of the Level 10 users clicks on Manage->Pages in the dashboard, she can't see any of the pages that I've (Admin) created for the original site, even though we both have the same permission level. Also, when she created a page (logged in as herself) and put the author as being "Admin," she couldn't edit or even see the page after she saved it.
So... I'm guessing that even though a user can have the same access control as an Admin, they still can't create/edit/delete any pages written by an Admin - even if they log in themselves and put the author of a page down as "Admin."
Not sure if this occurs with posts, but since I'm not creating any blog post content for the customer... I guess we'll have to try that. ;)