Comment A likely placebo effect (Score 2, Insightful) 652
There is likely to be something similar to a placebo effect (in addition to confirmation bias and other psychological pitfalls) that will reinforce the idea that this works for officials there. If they believe it works, it is likely at least some bombers will, too. So it has a deterrent effect that is likely measurable. Therefore if they do some correlation studies later, they are likely to find places that do use these will have lower rates of incident (as long as you don't compare to places with actual bomb detection).