All I can say is that they seem pretty hardy here in China.
The breeder I bought from has a 500 chick minimum policy. We were only able to buy so few because we drove there, and they thought it was pretty funny anyone would want to raise chickens in their apartment. When we came back for more they were astonished, and pretty excited to hear about the project.
They sure seem to have a solid breed.
Its not all that great for asthetics, but for hardiness, meat, and laying it gets a good rating.
Even when I was walking through the incubator and brooding areas it looked like a 1-4% loss rate from genetics, disease, or what have you. I was impressed.
Also a little jealous, I want a place like that.
Again I wish you the best of luck in stabilizing the breed, you could be very right about the conditions.
I just hope that's not the case.