Another four-legged addition???

Many of you know that we have a cat, named Rocky, who we got just after moving to Colorado a couple of years ago. And this March we added Toby, our little Chocolate Lab, to the household. We do not want anymore animals -- the two that we have are more than enough for us, and are a handful to care for already. However, any day now, I fully expect to look out the window and see a little Golden Retriever, named Kiley, standing in our backyard. Kiley is our neighbor's dog, and she is an avid digger. She and Toby have become fast friends. In fact, they have become such great friends that Kiley has decided that there should be a tunnel connecting our two yards. And while Kiley is the digging culprit, Toby has hardly been discouraging her efforts. I was recently throwing the ball for Toby, and instead of bringing the ball back to me, he walked over to the tunnel Kiley has been digging (Kiley was standing on the other side of the fence, watching us), stood over the hole, and dropped the ball through to Kiley. She proceeded to grab it and run away. I think maybe they have some sort of toy sharing agreement between the two of them that we are unaware of?? Below is a picture of Kiley's efforts -- she can only fit her head and front paws through now, but I do not underestimate her ability to tunnel into our yard.