And this is a bad thing because...?
Forgive me, but I personally cannot fathom why it should matter to you whether they hatch the eggs or not. After all, you're getting paid either way, so I fail to see the detriment if they decided they wanted to try hatching the eggs. Once the transaction is...
Cat purr sounds are probably an indication of contentment, much like with an actual cat. My chickens make the same sound sometimes, and they are all perfectly healthy.
Recently signed a pledge to refuse cage eggs, in order to help free future battery hens from the daily horrors of their existence via the following link:
http://www.animalsaustralia.org/no-way-to-treat-a-lady#pledge