Without searching for it I think they said it was in granule form as opposed to a solid block
I suppose granules could "leak out" of folded meat.
I don't know much about either TBH, but Aldicarb, the bible tells me, In humans, the onset of symptoms is rapid, < 15 minutes
LD50 = 0.5 mg/kg to 1.5 mg/kg when administered in a liquid or oil form. The toxicities of the dry granules are distinctly lower (LD50 = 7.0 mg/kg),
1000mg = 1g so a 30Kg dog, would only need to consume 1/4 of a gramme for its life to be in the balance.
Carbofuran is highly toxic to vertebrates with an oral LD50 19 mg/kg in dogs. again not even a gram to make the dog extremely sick, and its life in the balance.
Both are known to be particularly toxic to birds.
And the fact that its HIGHLY toxic to birds, makes me wonder if it was an attack on wildlife rather than a dog.
But as you said, its a "none UK" event, so I guess we will never know, apart from searching the various dog forums.