Legal Question in Legal Ethics in California

If the contractor is unlicensed, the driveway is a free gift even if the correct driveway was paved. My best guess is that a licensed contractor would also be rendering a free gift to the neighbor in the circumstances you mentioned, since the neighbor did not request the work. The neighbor might not want, or might claim not to want, the pavement, for example if the contractor tore up his brick driveway, and might demand money and/or restoration of the property to its previous condition. Either way the contractor eats, at best, the cost of the work.

Why was the wrong driveway paved? Maybe it was the customer who put down the wrong address.

Liable to whom for what? There's no way to answer without that.