Central admin-managed contact list for iPhone

what is the solution to provide a group of iPhone users (personally owned devices with users own AppleIDs) with an group-contact list that is centrally managed by an admin (i.e. the group contact list on phone always being sync'ed with central admin version)? E.g. consultants in a workgroup being able to get hold of each other and ensuring contact list is always up-to-date.

Most existing contact-related apps don't seem to have admin/sync functionality to other accounts, just like they try to sync with contact list on the phone which should be an option but not a requirement. (examples on contact list are: ContactSync, Contacts Sync, Get Contacts, Circall, ContactBox, ZXContacts, aContacts+, ...).

A Google account and Contacts could be used for "admin service".

I have been unsuccessful trying to set up Google to delegate contacts, though this may solve some issues.

Has anyone had the same challenge before?

Thanks!

Rune