Notoriously unmaternal hen went broody a few weeks ago and I popped 7 eggs from my auracana/RIR cross hens under her, not expecting anything to come of it.
Went down this afternoon to discover 4 hatched, two under mum and happy, two halfway across the coop but cold, glassy-eyed and fairly dead-looking. No idea how they ended up across the coop. I picked them up, they were stone-cold but I thought I saw a toe twitch on each, so popped them back under their mother on the grounds that you never know.
Two hours later, they are alive and perking up, glassy-eyed no longer, and tweeting. Amazing.