On feeds, how to access ORGANIZER source
In writing the question I came across the answer and want to share. I was using the wrong hook. Instead I used: 

function my_hook_date_ical_mapping_sources_alter(&amp;$sources) {
// Add the "ORGANIZER" iCal property to the mapping sources.
$sources['ORGANIZER'] = array(
'name' =&gt; t('Organizer'),
'description' =&gt; t('The ORGANIZER property.'),
'date_ical_parse_handler' =&gt; 'parseTextProperty',
);
// Add "ORGANIZER:CN" parameter to the mapping sources.
$sources['ORGANIZER:CN'] = array(
'name' =&gt; t('Organizer: CN'),
'description' =&gt; t("The CN parameter of the ORGANIZER property: the organizer's Common Name."),
'date_ical_parse_handler' =&gt; 'parsePropertyParameter',
);
}


Note that I'm pulling both the Contact's Name and the mailto field.

This is a hook provided by the date_ical module. I basically copied the example found there.