Hmm, perhaps the external consulting precludes the idea entirely, but no there is no example. We have only recently established this concept and given Guilds a one-time pass to transform themselves into the Department style of funding, vs member funding. See: Member-Based Guild Funding
Likely there is not much difference in funding mechanics: Departments must give an accounting of roles & expenses, but the label does help defer any type of “self sufficiency” KPIs in favor of ones that orient the group towards simply serving the internal needs of the DAO.
Since there is no example of a project turning into a Department - or the creation of one on its own - we can chart this course on our own using classic proposal consensus. Forum > Snapshot.
cc @links for insight and possibly the procurement of specific documentation the effect of “How to Create a New Guild or Department”