I am not sure if they would let you rescue them, they send them off to slauter when they stop laying. But by all means try. It is very sad, they don't have any beak left. Here is a picture I took on an animal santuary in Vacaville. These birds are sooo sweet. This girl has to be hand fed grapes because she can't use her beak.
I had a friend who got some Battery Hens cheap. Be prepared for what may come with them. His would never roost, they never learned how. Or use the nest to lay their eggs in. They had combs that laid over.(from cramped cage conditions)And they refused to come out of the chicken house. If he brought them out they would run right back in. It was a very sad sight to say the least.
They had very shortened lives,even though my friend went above and beyond to help them.
A friend of mine told me that the local egg farm (Wilcox, if you're near me) sells its battery hens once a year for $1 each. She got a couple one time and had to eventually give them up because they had such a hard time eating that they got too skinny. That might be fixed with deep dishes of food, but it might now.
I agree about heritage breeds being potentially more rewarding.