First, at the admin account (or other account), create a Shared Contacts folder in the address book view of :
The commands to share it with sam1@example.com would be:
# grant manager (rwixd) rights zmmailbox -z -m admin@example.com mfg "/Shared Contacts" account sam1@example.com rwixd zmmailbox -z -m sam1@example.com cm --view contact -F# "/Shared Contacts" admin@example.com "/Shared Contacts"
Now you can use scripts to bulk set it up.