CB uses their own mailer API. I ahve received the following answer back from the CB guys. Is there any easy way to integrate CB api into CMandrill?:
CB has its own mailer API. No, CB has no option to use Joomlas (nor is one planned at this time). CB provides CB triggers to override our mailer API so your integration would need to use those triggers to do so. No, CB Auto Actions can't override our mailer API and you'd just end up with double emails. Specifically the below triggers are for our mailer.