Answer: I'm afraid it would be impossible to transplant full-grown trees. The root systems are so extensive, and the tree would be difficult, if not impossible, to transport. Remember that a tree's roots roughly mirror the size of the tree's canopy--so the rootball would be almost as large as the top of the tree! (The roots usually extend out to the tree's "drip line", or the circumference of the tree's crown. The roots usually don't go as deep as the tree is tall!)
I assume you mean trees that are more than 20 feet tall. If they are smaller than this, you might call your city's parks department to see if they are interested. But the cost of removal and planting would be large--if you're interesting in donating the cost of the services, they might be interested.
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