You are right! I don't see a reference to it on theAMEX site either. I had gotten an email from AMEX with this promonotion and a link in it. Will check to see if I kept it and then see if I can post a link.
Found further info on the AeroMexico site at:
http://www.aeromexico.com/ingles/clu...mp/prom_mp.htm
Don't know why I can't find anything on the AMEX site, I know the email came from them.