On a whim, a friend of mine dropped the $29 with
www.aircourier.org, just to see what the deals were really like.
I poured over the whole package he got, and nowhere was there mention of FF miles. So while it's pretty ambiguous, there is a significant amount of stuff that's left up to the particular companies the courier actually does the run with -- there may be different policies and room for negotiation there. But he hasn't tried a run yet, so I don't know what will come of it.