Phones pull their phonebooks like they do their config files, so this is probably going to be a job for EPM.
Getting the local directory data from the server into the phones usually involves some kind of an extract and reformat program. The Yealink will use a different format than the Sangoma phones (see Yealink XML Phonebook.xml auto-generation for more information).
Someone from Sangoma may want to chime in here at some point - I don’t know what they do/require when it comes to preloading directories.