Those files do NOT need to be in the Auth folder.

To share Admin/Users just make sure that the .cfg files for the shared datafiles say the same thing at the following part of the .cfg files (use a single default.pass file).

# Full path and file name of the authorization directory.
$auth_dir = $db_script_path . "/auth";
# Full path and file name of the password file.
$auth_pw_file = $db_script_path . "/default.pass";

I would not share the counter file, unless you have some reason, sharing the log file maybe, but you may not be able to tell which database they were editing unless the log files are seperate.