I don't see the AB as quite pulling off a hit like that. It is possible, but not probable. Cartels are really into demonstrating that they have their tactical game on these days, matching SWAT outfits, by the book getaway plan. Smells like Zetas.

What is entirely possible is the AB people called in some favors to get the thing done as a condition of doing business with the Zetas or some other cartel looking for new crews to run their operations in some of the white only areas. That was roughly the theme on the Miami Vice remake movie a few years ago if I remember correctly. AB working with a foreign cartel.