The 2015 MKC came with 2 YR/24 Complimentary Maintenance. I took possession on mine in early Sept 2014, I made sure I got my last "free" maintenance done in Aug 2016.
However, I have gotten the special price maintenance letters from my Ford/Lincoln dealer at various times in the past. I suspect they don't particularly care if you are under a maintenance program or not. If it gets you into the dealer for the maintenance and it turns out it is free to you, they just get reimbursed from Ford/Lincoln. Either way, the dealer gets paid!
I suspect some dealer may not bother sending out maintenance letters. There is a cost to do that. If they have little competition in their area, they probably don't need to spend the money to get you into their shop.