Hi there,
An extension can be restricted to see only its own recordings, or all recordings.
This can be done through the extension properties / Options tabs / tick "Allow 3CX Management Console Access", then ""Allow 3CX Web Reports Access", and "Can download any recording" or leave unticked for own recordings only. Login is the extension num and password is the one generated in field "Access Password for 3CX Web Services".
However I'm afraid you can't restrict access to recordings of others extensions or a group of extensions. Please post this as a feature request on 3CX Ideas : http://www.3cx.com/ideas