Interesting, indeed!
I would visit the owners again -- ever since other apartment dwellers, the Humane Society and the landlady got involved, the consequences for the grey cat have changed. The stakes are higher -- being 'im-pounded' is a threat as bad as freezing. They may not be fully aware of this. Knowing this, they might agree to give you the cat, if you can let it in and out more, or they themselves may begin taking better care of it.
Also, if you do obtain the okay to adopt the cat, its habits will likely not change. She's an outdoor cat who will continue trying to get out. If you want to keep her indoors, it takes about 2 years for a cat to accept this.
It strikes me that, like the cat's colour, the answer to the problem might also be grey. :) Does there have to be one owner? Can you work out a cat co-op, or time-share? Bet the 'owners' would love a hand in paying for food, litter, and vet bills.
Whatever happens, it might be very neighbourly and good for consensus to have somebody (you? landlady?) post the decision or proposition so everybody knows -- perhaps other unit dwellers are equally concerned about the cat's welfare and might be happy to let her inside, or get more involved. It would be lovely to have a cat that belongs to a whole building.
Lunarreikin
