The Chameleon extensions allows administrators to trigger different actions based on large number of conditions. This extension makes use of Joomla! routing mechanism, by adding some parse rules, just like sh404SEF.
It appears that to operate properly, the Chameleon system plugin should be located after the sh404SEF system plugin. However, when set this way, Chameleon rules cannot be executed on the sh404SEF 404 error page.
This behavior has been experienced with version 2.48 - July 2015.