Flights partner airlines made available to CO are city pair specific. This is true for revene tickets or award tickets. Interestingly, I have only heard of it for flight either to NRT or through NRT.
So, cut CO some slag. AM will only let CO ticket MEX-NRT and not TIJ->NRT. There is nothing CO can do about it.
AM can not change any routining issued by CO; revene or award tickets. I had a trip with all Air France revene segments. AF can not changed the routine because I was silly enough to let CO issue the tickets.
Nancy