Would it not be easier to get permission before hunting season has started. Talk to them before season and ask them if it were ok to get an animal if it were to cross the boundry line. I have an agreement with the land owner next to me that if they shoot a deer and it goes on my land, please check for my vehicle by the cabin. If it isn't there that means I am not hunting and they should go get there deer. If my truck is there then they should wait (because I am hunting) and when I get in I will help them find it. But if I did not have that option I would probably go and get it. Even though I know that it is not ethically right, I would have a harder time sleeping at night if I didn't recover that animal