A point that we should not miss which can be inferred from the article - Mexico is MUCH stricter with illegals on its southern border than we are on ours, exercising an incredible double standard when complaining about how we restrict their citizens trying to cross into the US.
Seems to me that Guatemalans and others heading north were fine - as long as they traveled all the way THROUGH Mexico on a US-owned and operated rail system. Now that their passage isn't so fluid and they might actually have trouble getting to the northern Mexican border, Mexican officials have begun to give them a much harder time - hence the boats.
Mexico throws fits concerning the "abuse" of theirs trying to get into the US, but Guatemalans et al - don't you dare enter Mexico illegally.
That caught my eye too. But Mexico raises a fuss if we do the same thing.