So it seems imagick (the php module) does not call imagemagick (the commandline tool) but does appear to require that it be installed. My assumption is that imagick has dependencies on certain dylibs included with the imagemagick installation. However they are not linked as I had previously expected and thus I overlooked this dependency when originally crafting the build scripts for it.
I will continue tracing this through later this week. Apologies for the oversight and thanks for your patience.