The guys who do this professionally/successfully in a sparsely populated place with everyone helping and the advantage that rats can't survive outdoors don't think it's possible in cities.

Big problems with poison: Rats are harder than you think to poison, they're both sceptical of new food and adapted to survive lots of poisons Evolution will work against you and select rats that don't eat or digest your new poison You will poison lots of things you don't intend to (wild animals, pets, humans).

You can imagine an IOT solution in 50 years though (coordinating web of mechanical cats/ferrets with amazing smell/sight that just never stop hunting).