Parallels Plesk Panel version 11 has its own PHP selection functionality. More information you can find on the following link: http://download1.parallels.com/Plesk/Doc/en-US/online/plesk-administrator-guide/index.htm?fileName=72042.htm
It is fully compatible with our PHP Selector and CageFS. What happens is that Plesk selector switches 'native' PHP version, while our PHP-Selector switches site to alternate PHP versions.
If you install different PHP versions from the link above to activate it for the customer you are required to run:
# cagefsctl --force-update
Resellers have no control over PHP-Selector, and shouldn't have any. Only admin & end customers have control over PHP-Selector.