I'm busy writing a plugin, and came across the following behaviour:
As per codex page http://codex.wordpress.org/Plugin_API/Action_Reference/admin_head-%28plugin_page%29 you can hook into the page
<head> tag for your plugin page.
If the plugin submits to itself, with the GET variable
noheader, and then manually includes
wp-admin/admin-header.php, the hook doesn't appear to run.
I can't seem to find any official documentation on
noheader, so I didn't want to post this straight to the trac