moving away from feral community

My sister and her husband have a business in a Seattle neighborhood with a
large feral cat community. They have been taking care of this community for
about
10 years, feeding, vaccinating, spaying, neutering, nursing and finding homes
for kittens etc. They are now needing to move their business to a larger
building in a new neighborhood, and can't find any information on what they can
do for the remaining cats, now that they will no longer be around to take care
of them. The vet they asked responded with a very helpful "I dunno." Any
ideas would be very welcome.Thanks. Susan C