How deep would the tap roots be on a 15 year old Bradford/Aristocrat pear tree be? and how difficult to pull out with a half ton 4x4 truck?
Helped a friend with a massive old peach tree. We dug down over a metre in about a 2m diameter circle around the trunk. You could tell where the rootball was as you dug. Then chucked a rope around the trunk and hitched it to the towbar of her little 4x4 suzuki. Came right out. Really depends on your soil. If you've got pretty soft soil the root ball may be quite deep. If it's hard, like clay, there may be more lateral roots than downwards roots. Should be doable either way as long as you've dug far enough and all the way around. You can also smear some honey on any feeder roots you need to sever to prevent bacteria getting in.. if you're planning to transplant anyway.
Know anyone with a backhoe? That or burning it out are the easiest methods.