Smarty is run by Apache.... Apache is run as a Daemon.... the Daemon doesn't belong to a group.... thus Apache doesn't belong to a group.... thus Smarty is run as "no group" and "nobody"....
You could change Apache to run as a Super User, or a user with access to all /usr/*/public_html folders plus your PHP and mySQL etc. essential files.
Or you can try using the FTP functions to chmod the files via FTP....