I agree with those who have said that it is much better to focus efforts on the cats that you know still need to be altered. Remember that spring will be here before we know it and tragically, 3/4 of the kittens who will be born to the unaltered cats will die before their first birthdays. The most important thing you can do to prevent more suffering is to get the rest of the colony altered before spring and ideally before the cold weather hits. The females will start getting pregnant in significant numbers in mid to late January and that is right around the corner.
As to your question about getting them to trust people other than you, it is impossible to say for sure but getting a feral cat or even a former feral kitten to trust anyone other than their primary caregiver is by far the hardest and most time consuming part of the job and it may not ever be successful. Some may surprise you and take to strangers without much fuss but they will be the exception.
From my experience, I have known a fair number of adult feral cats who have been able to live comfortably and reasonably happily in their original caregivers' homes. But I haven't personally known of any who have been able to become realistic candidates for adoption by others. Even though many of them probably would ultimately do okay if adopted, it can be hard to find adopters who want to adopt even the friendliest adult cats. And since these adopters can have their choice of many, many friendly and sociable homeless cats from shelters and rescues and even "free to a good home" ads, not many of these people will gravitate toward cats who are fearful of humans. There are some people like that out there, of course, and God bless them. (Though tragically these "hard luck" stories can also be a lure for hoarders, so careful screening of prospective adopters is in order.) But these wonderful people are a rare type and meeting one of them is probably not something you can depend on.
For the cats, let them go back to their home. If they could talk, it is what they'd ask you for. A cage is about the scariest place in the world if you are a feral cat or other wild animal and an adult or "teenage" feral should not ever be caged unless it is medically or otherwise absolutely necessary (like for TNR and recovery from surgery). Even then you have to take steps to reduce the cat's stress or his health can be significantly compromised. This is mostly done by keeping the cage covered and keeping noise and intrusions to a minimum, and by keeping the time the cat is caged as short as can be realistically accomplished.
For another perspective, here is Alley Cat Allies' official "position paper" in the subject: http://www.alleycat.org/pdf/TNRnotTNA.pdf