Pretty ingenious. I have to say I am impressed. Yet the questions are: !.) What if some not drug smuggler parks there and thwarts the efforts of the day? What then? What happens if some innocent victim sees something. Do they off them? As a writer these are the questions I would be asking in my novel. Sometimes truth is stranger than fiction in that a written or reader/viewer may find it had to believe. This one does pass the test though. It was obviously incredibly affective. Well you gotta give it to these people they do whatever it takes to make a dime. Just very bad morals etc.
I would wonder what that big slice of cement is though.
Don't know if you have ever read any of Tony Hillerman's books but he wrote one that has a very similar senario. The name of it is "The whistling Pig" I believe, something like that, has been a while since I read it.
It is about drug smugglers using an old oil line to smuggle dope into the country using the cleaning pigs to send the stuff across the border. Also I have seen several old movies where something similar went down in relation to bank robberies.
An enterprising intelligent leader of these vicious jerks probably picked up on things like that and came up with his own version.