First up, an article about this: https://www.greenmatters.com/news/2018/02/19/2m3wbf/border-collies-forest
It doesn’t give much more info other than looking at the share scale of the destruction and the speed at which the doggos can cover the terrain! Looking into it a bit further it’s clear that when fires are this intense, they can sterilize the soil, destroying not just the trees/plants but also the seed bank and mycorrhizal networks that help forests regenerate. Plus, by choosing the seeds they spread they can convert areas that were overtaken by introduced species back to native ones. Natural seed dispersal can still happen by wind or wildlife but this can be much slower meaning regrowth is delayed meaning soil erosion can occur. Not all heroes wear capes, some wear leeetle backpacks!
The way I assume it works is that the humans walk a trail or in a particular direction and the dogs run out from that trail several hundred metres to the left and right, massively increasing the coverage area.
This breed of doggo is highly intelligent and highly trainable. I don’t know to what extent these ones have been trained but Border Collies can be trained to operate with remarkable precision, basically like they’re remote controlled. Look up any sheep dog trial videos for good examples of the intelligence and precision they are capable of working at. They can both follow complex commands and problem-solve on the fly and even be taught to avoid flagged zones that you could mark as you go, which might be areas with delicate new growth or sections that have been covered already.