Here is a translated excerpt from Gustavo Castillo García's article in the Mexican daily La Jornada:
"The arrival of members of La Familia [Michoacana] to support the Gulf Cartel in its dispute against [Los] Zetas in Tamaulipas is the cause of the clashes and dissemination of messages that have led to distress in the population of the towns of Reynosa, Matamoros and Rio Bravo, said federal government officials involved in intelligence activities in that state. According to sources, in the last two weeks, the Gulf Cartel has begun using the same measures of social persuasion that La Familia has used in Michoacan: tell people in its operational areas that their activities will not affect the population not involved with rival groups, and, on the contrary - even though it involves criminal activity - they will protect the local community and support economic growth in the region." Link to Full [Translated] Article
Analysis: There are two significant things going on here: first, the split between the Gulf cartel and Los Zetas. Second, the involvement and quick entrenchment of La Familia in that split.
I think most observers of Mexico's drug war were waiting for that split to happen. For those of you not up on cartel background, Los Zetas used to be the armed wing - or hired hitmen - for the Gulf cartel. They are extremely well-trained (former Mexican special forces soldiers) and well funded, meaning they're quite good at what they do. Ever since the former Gulf boss Osiel Cardenas Guillen was extradited to the US in 2007, the Gulf cartel has been picked apart by the Mexican authorities, and Los Zetas have gained an increasing amount of control and influence in the organization. Eventually, Los Zetas split off to become a DTO in their own right, while maintaining strong ties - and mutual interests - with the Gulf cartel. The new organization was being referred to as La Compañia, or The Company, and took into account both organizations - much like the Sinaloa Federation is a compendium of several mini-DTOs.
Then the inevitable happened. It looks like Los Zetas were ready to take a bigger share of the drug market in Tamaulipas, and decided now was the time to wrest that away from a weakened Gulf cartel. Unfortunately, that's causing a lot of problems in Reynosa and the surrounding area for its residents and Mexican law enforcement. There have been a record number of firefights in the last week between Mexican authorities and DTO members in the area, and until the Gulf and Los Zetas can get things hashed out, the level of violence is bound to remain elevated.
As if that weren't bad enough, it looks like La Familia Michoacana is getting into the fray by backing the Gulf cartel in Tamaulipas. This is really interesting for a couple of reasons. First, geography. Take a look at the map below, particularly at the areas of influence for La Familia and the Gulf cartel:
La Familia's area of influence is landlocked and very small. They deal almost exclusively in methamphetamine, reportedly responsible for trafficking half the meth that enters the US from Mexico. La Familia has also taken massive hits from the Mexican government in the last year, significantly affecting some of their operations in certain areas because of their smaller size. From a strategic standpoint, aligning themselves with another organization that has also been taking hits - the Gulf cartel - and offers an opportunity for expanding beyond the meth trade (the Gulf deals in cocaine, marijuana, and heroin on top of meth) makes good business sense. Los Zetas have also been trying to work their way into La Familia's territory and operations, so it's just as likely a defensive move as well.
The alliance is also interesting because La Familia Michoacana is really a strange cat as Mexican DTOs go. They're almost like a cult, and are deeply involved in communities in ways that other DTOs are not. I have no idea how Gulf leadership might receive some of La Familia's ideas or methods, given that the Gulf is a traditional organization as Mexican DTOs go. But should the Gulf cartel choose to embrace La Familia's evangelical methods, it could make the resulting hybrid between the two DTOs into a challenge the Mexican government isn't prepared to deal with. I say that because La Familia is entrenched in all levels of society and government, commanding an almost religious following from those loyal to the DTO and the utmost deference from politicians under its control. Some may have thought them manageable when "restricted" to the state of Michoacán. But should the Gulf choose to engage in similar activities all along Mexico's eastern coast, we may see an unprecedented level of DTO involvement in society in politics that the Mexican government cannot provide an alternative for.