@Swimpy,
Virtually all TNR (trap-neuter-release) programs will vaccinate for "distemper" (really herpes, calici, and panleukopenia, usually) and rabies at the time of surgery.
Honestly, cats are not very susceptible to rabies, though if someone is bitten by an unvaccinated cat the legal requirements for quarantine are still fairly stringent. This burgeoning colony would be a prime place to see a panleukopenia outbreak, though.
A concern that you might bring up if the conversation can be restarted is that outdoor cat colonies also are susceptible to infection with FIV ("kitty AIDS") and FeLV ("feline leukemia"), and risk of transmission of to neighborhood cats increases with the size and sexual activity of the colony.
Good luck. I've plenty of experience dealing with cats from hoarder situations, and they tend to start out just like this. I'm glad you and the neighborhood are trying to nip things in the bud -- the longer it goes on, the less the likelihood of getting everything under control without a large loss of kitty life.