setting acl on autocreate folders

[Jean Charles Delépine]

Hello,

I'm playing with autocreate mailboxes but I can't find a way to set
extraneous acl on the created mailboxes.

My users intensively use plussed addresses and they want those plussed
mail to be delivered in the correct folder.

This, to be achieved, needs the acl anyone:p be set on the INBOX (that will 
be inherited by its subfolders on creation).

defaultacl is only for non users mailboxes
implicit_owner_rights is only for owner acl

So, is there a way to automatically set acl anyone:p on newly created
user mailboxes ? 

Sincerly,
     Jean Charles Delépine