The rabbit-proof fence ran right through Australia, from north to south. It worked so long as the governments paid for stockmen to patrol it, keeping it in good order, but more importantly stopping rabbits from burrowing underneath it. Eventually, rabbits did get through and governments were less willing to deal with a problem that had simply become endemic (the rabbit-trap salesmen would typically visit a farm twice - once to drop off a breeding pair of bunnies, a few weeks later to point out the problem the farmer may not have noticed and offer a few traps at a really good price).
However the toad-proof fence is different because it is used on a much more localised scale - each farmer would fence off his own dam. Secondly, and a key difference, it would still work in an area that has been infested because it denies the toads the ability to breed.