I have set my cron job in cpanel for:
*/15 * * * *
php-cli -f /public_html/owncloud/cron.php
In ownCloud settings it seems to be running and updating every 15 min as intended but I never receive an email reporting the events.
What exact email do you expect? The cronjob doesn't send mails, there could only be mails from the notification app. If you mean that check your logfiles if there are any errors related to a failed mailing process.