What you say could easily work. In fact the fianal transport of the container or multiple containers need not even be under the control of any person who is involved in the plot in any manner. The GPS trigger would entirely negate any need for personal involvement. If it went off on a freight car that was part of a train carrying other hazardous materials likew say Peopane, LNG, methyl Isocyanate or any of a number of other routinely transported substances the devastation would be even greater than originally planned.
Even simpler would be a suicide bomber aboard a ship carrying an explosive cargo. He merely defeats the safety systems and boom. As an example take an LNG tanker where the valves are opened so that the LNG is released to the air and then the bomber flicks his bic. It is as cheap and simple asit gets. large quantities of LNG are exported from the Arab nations and an Arab aboard such a vessel would attract no attention.
Stay well - stay safe - Stay armed - Yorktown
Remember last year when a train loaded with HAZMAT crashed and burned in a tunnel under Baltimore? Imagine an ANFO container bomb in the middle of that HAZMAT cargo, going off "contained" in a tunnel under a city.
Are they bringing LNG tankers back into the terminal in New England? I know they suspended that for a while. Would LNG really explode, or just burn back to the tank, and then gassify the LNG as it came out and burn in a spectacular fashion?