Read the article. Says it only takes 5 minutes to train them, something about mixing food and explosives. They associate explosives with a source of food. The trainer stuffs them in a piece of PVC pipe with a screen covering, starve them for a day or two, then they go crazy when the smell explosives/food. It didn't say anything about how they could tell the difference in response to explosives, and Bar-B-Q and Beer (normal diet I guess).
Anyway, that research was suppose to be published here last January, guess it wasn't as exciting as in the UK...