Property line/tree neighbor question

[testcase]

I've been told by a "Tree Guy' that OAK trees send down a "TAP ROOT". Said tap root basically grows straight down to "anchor" said oak tree. Of course, as the oak tree grows, so will the tap root. It would be prudent to speak with a KNOWLEDGEABLE PROFESSIONAL (licensed arborist or staff at your "County Extension" if one exists where you are).