If the copier has a Bind DN option, then something along the lines of...
access to dn.subtree="ou=Engineering,dc=example,dc=com" by dn.exact="cn=EngineeringCopier,ou=Engineering,dc=example,dc=com" read by [...everythingelse...]
access to * by dn.exact="cn=EngineeringCopier,ou=Engineering,dc=example,dc=com" none by [...everythingelse...]
If it doesn't, you could substitute the "dn.exact" with "peername.ip." Super disgusting, but it'd probably work.
(NOTE: if you're going to write back "they're all in ou=People" try
access to dn.subtree="ou=People,dc=example,dc=com" filter="(dept=Engineering)" by dn.exact="cn=EngineeringCopier,ou=Devices,dc=example,dc=com" read by [...everythingelse...])