WARNING
This comment is pure speculation.

I was talking to a friend of mine who is going for a masters in political science. He thinks that the attacks were by drug cartels. The drug cartels are threatening the infrastructure to get Mexico to back off from their recent crack down.

If perpetrated by a drug cartel the attacks would be professional and no one would claim credit. It would not be in the interest of the drug cartel or the president to make the facts known to the public. If the public found out who was responsible they would demand a harder crack down which would cause more attacks and cause political damage to anyone in office.

I don't know anything about Mexican politics or drug cartels but it seemed like a good explanation to me so I am passing it on.

Tim

More pure speculation: the attacks were Venezuela dredging up the ghost of a long inactive revolutionary group to damage Mexico's economy and perceptions of Mexico as the safest place for FDI. Even if it isn't true, it makes a good story to get people motivated to do something about Hugo... I seem to remember something about Yellowcake?