Of course they'll check with CBSA, and that will be the biggest determinant of whether or not you clear the eligibility requirement. Employment is not a requirement.Do you think they check CBSA report first before they start checking if you were employed or not. I was unemployed for some months and I have never step a foot outside Canada since I came here, but still I still get worried because logic seem to be far from CIC's reasoning.
I can't tell you how the CIC works either because they really show little consistency and fairness in their processing, but as long as there are no inconsistencies between the info you put in your application and what they pull from CBSA and CRA, you'll be fine. Also no gaps in your history and addresses and no shady addresses (like P.O. box addresses). That's it really...there's no reason otherwise why your file would be delayed or rejected. Absolute worst case is you get CIT0520 or RQ and that's not the end of the world nor does it happen to one class of applicants over others. There is no method to the madness of the CIC!