When "Interview recommended" first appeared in our notes, I called the CIC helpline and was told that usually with a "recommended," your application will be reviewed by the officer's peers and/or superiors, seeking consensus on a final determination - When the later notes change to "interview required," as it did with us.., then you are put into the waiting queue - which for us was not updated in ECAS until after we faxed the Embassy for an update and received the actual interview date via email. I'm not absolutely sure, but it seems the scheduling for all of this was at least somewhat governed by the outside limits of the 'medicals' expiry date, which gave us about 2 weeks to land before having to redo that.
This is the quote I find from the forum.I hope it give us some information