Here in Las Vegas, NV we have a city/county wide TNR program (trap, neuter, release). There are tons of volunteers city wide that actively trap feral cats, they are given shots, spayed or neutered, groomed if needed, ear mites treated etc, and then they are released back to their colonies to live out their lives. The tip of the right ear of the cat is clipped to show that it has been fixed. There are many volunteer caretakers that feed these colonies. The city now even has a new law that if you register the colony you are caring for, if one of those cats are picked up by animal control, they are returned to you.
A year ago a stray cat showed up in my yard and had kittens. She wasn't a feral cat, she was one that had apparently been abandoned a year before due to a home forclosure in our neighborhood. We of course fed her while she was nursing the kittens. When the kittens were old enough, we trapped them and the animal foundation took them in to be socialized and find them homes. We then trapped Momma Cat and brought her to the place that does the TNR program. The cost was $25 to me to have her fixed and get shots. We took her home and locked her up in an empty room for her 48 hour post surgery care. We were told to release her where we trapped her at and she would rejoin her colony. Funny thing is that she never left. I have tried to make her an inside cat, but she doesn't like coming in the house with my other cats, and they dont like her. She lives on my back patio, sleeps on the patio chairs or in our tool shed (which we now have to leave open for her). She has plenty of food and water, and even a potty box inside the tool shed. A few months ago we even took her to the vet because she developed a urinary tract infection. For the past month or so, two of her feral friends have been coming around for dinner. One of them is sporting a brand new clipped ear, so I know he has been fixed. I have to borrow a trap and try and catch the other one so I can get it fixed too.