JonStobbs, I will defer to others wisdom on this as I cannot say I have ever used ATF, but I have spoken to a few that have and they said it works - how well over long term I don't know. I agree it would likely be too low viscosity in hot climate, but in cold climate ATF may be the only automotive oil thin enough and readily available?
Parkie, I agree gearoil would logically seem like a good choice, but 85/90 is much higher viscosity than scottoil. Thats OK as long as you have enough adjustment range on your oiler. My oil resoivoir is mounted low and I doubt I would have enough adjustment unless it was way hot outside. Oh, and gearoil smells bad, but I guess you do what you gotta do if you have limited choice. Any of these oils on your chain is better than no oil - I think.