(Separate post because it's my opinion, not the question posed in the OP)
My family has a large ranch, and they maintain a barn colony that's been around for a long time (longer than my mom's been alive). The purpose of the colony is to control rodent populations around the granaries and barns.
Currently, the population's around 10-15 cats. The animals are moderately socialized (most will greet you when you enter, 4 or 5 are allowed in the house). All the cats are s/n, and the population is maintained when new cats wander in (or are dropped off). Vet care's minimal. The cats have free access to dry food, running water, and the barn is heated year-round. Not all the cats have names, and for those that do, it's a toss-up whether they respond to their name.
This is Sam, the 'alpha cat'
He's about 12 years old, I think (I remember him as a dapper young Tom around 2001/2001). Obviously he's not in peak physical condition and his life hasn't been easy, but he's earned his keep and a spot inside whenever he wants.
That was a long ramble (because I'm bored at work), but... For me, I think working colonies/populations have a place in the world. I much prefer using a 'natural' solution for pest control, compared to Warfarin or other poisons/chemicals. However, I recognize these are "working" cats, not "hobby" cats, if you can put it that way. They exist to be useful, and there's a certain consideration of return on investment when it comes to their care. Much like a horse or oxen on a "real" farm versus a "hobby" farm, when injury or illness happens, you have to consider the $$$ of upkeep versus the usefulness.