The attached archive contains a very small addon that should die/print the filename of the controller when installed and accessed via:
<admin_url.com>?dispatch=x.test
In reviewing the code, it does not appear that the fn_install_addon_templates() function installs an addon's mail templates into the design/frontend/mail/addons/ directory.
I must be missing something becasue I can see where other addons have their templates installed. Shouldn't the code indluce something like: