I think (and hope) you're right that this is a straightforward application of the poisonous tree doctrine, but you should be aware that the doctrine is not quite a clean-cut as you make it out to be. One big exception to it is "inevitable disclosure". If a traffic stop is otherwise lawful, and a normal police officer acting in the lawful confines of their authority would have otherwise discovered e.g. the drug stash in the car (for instance, because it was in plain site in the back seat), the Poisonous Tree doctrine probably doesn't exclude the evidence.

That's the tricky thing about the Reuters DEA revelation. Some drug offenders probably are cavalier about displaying evidence in the cars because the likelihood of their being stopped is low. Here, domestic surveillance is allowing the police to drastically increase the odds that they'll make a fortuitous traffic stop.

What would not work, in my understanding of the story, is for an intelligence intercept to establish the legal basis for stopping and searching a car.