We have that program here also. There are 4 cats in the area and we put out water when its hot out, and a little food in winter to assist. In addition to the notch in the ears to ID them, they also get their shots and they are registered as "neighborhood cats"
They do seem to keep other animals away and keep rodents down. One of them even likes us enough that she will come up and meow at us for a belly rub.