The spirit of the school district "rules" are "where the child sleeps at night." So just owning a home may not be enough. If districts are heavily impacted, such as Palo Alto Unified, they may follow children home to see where they live. In other scenarios, say with a gifted athlete, the eyes will also be very intense and a district may ask to see his or her bedroom, and look for evidence that the child lives there.
In other larger districts with less staff, it may be less intense like a letter home. Some people own a home in a district, rent it out, and still use it as the home address. In less impacted areas, you can ask for an interdistrict transfer and receive it.
The spirit of the "rule" would preclude the child attending either district and would point to the child attending the school in the boundary area where he or she sleeps at night -- but lots of things like this do happen all the time and especially now with budget cuts it could be expected that districts may police it less. Alternatively with budget cuts districts may police it more and allow fewer "loose" attendance rules.