Legal Question in Real Estate Law in California

I'd say, without further facts, that the attorney is probably wrong.

If roots or overhanging limbs from X's tree get into Y's yard, Y's remedies include cutting back the roots or limbs to the property line. This is a special situation under the general law of trespass to land, where ordinarily resorting to self-help isn't permitted, and a court judgment is necessary. The special rule allowing for self-help in cases of "trespass by tree" was created by judicial decisions, not by the legislature, and recognizes that this is a commonplace occurrence and has a relatively simple solution, generally not requiring filing and winning a lawsuit.

However, this special exception to the ordinary law of trespass comes with a couple of caveats. One is that if Y cuts the trespassing limbs or roots of X's trees back to the X-Y property line, Y is not entitled to recover the cost of having the work done from X. Y must bear the cost of his self-help remedy.

My answer is qualified because "further facts" might show that the trespassing roots did some significant damage other than just being present where they shouldn't have been. For example, Y could sue X for money damages on either a trespass to land or a private nuisance theory if the roots caused a paved driveway to lift up, or broke Y's house's foundation, or the like. But as long as it's just the roots' presence and not some substantial harm done by them, X has no liability to Y.