You can collect Airmiles through airmilesshops.ca. Just sign in there first and then select to go "shopping" at Fairmont and you'll get directed to their website to make a reservation. You'll earn one Airmile for every $20 you spend on your stay at any Fairmont property. It doesn't matter if it's a promotional rate or not.
I would have thought that the promotional nature of this rate would have meant it didn't earn airmiles, but I was wrong. I have the airmiles toolbar installed, which automatically routes me through they're portal, and I went back and looked at my statement. I received airmiles for the NFAF booking I made recently, so it does work. YMMV, obviously.
Michael