my sister has hens and she all ways wants cartons, not only are they used for the eggs but she uses the paper ones for starting plants for her garden, so yes it is all ways nice to give them back with some thing in them.
We have hens too and I have gotten the cartons back but never with baked goods, that would have been nice. I usually think since the gave me back the carton they wanted more eggs (which I give them more). Good luck
Speaking of chooks, my father's friend took three chooks down to the place where they,.....well,...they go to the after life, a huge chook place here in Toowoomba. Well he was supposed to get them back whole for roasting, but they accidentally put them through the mincer, so they gave him 8 new chooks to compensate.They were the worst chooks I have ever eaten. You had to slice them with a chain-saw that is how tough they were. These chook places can't be trusted ROFL.