A two-fer, toll for the illegal to use the tunnel is to carry a load of dope.
From what I've read about the war on our southern border it goes something like this: "Paco, carry this package north and give it to our friends or you will never see any of your family again."
These Mexican drug cartels are every bit as ruthless as AQ or any other terrorist organization. Meanwhile, our gubmint keeps ignoring the problem. Makes you wonder what side the gubmint is on, doesn't it?