micky wrote:

Next door neighbor B installs or replaces cement driveway, right
next to their (A's) blacktop/asphalt** driveway.

For the forms, the contractor uses 2x4's and stakes them by
pounding stakes into A's driveway.

If the asphalt driveway is that close to the new concrete pour, to the
point that it's butting up against it, then there should have been no
reason to put up a 2x4 retainer. The border edge of the asphalt
driveway would serve as the retainer wall for the concrete pour. I've
seen it done. You'd want to match the height between the driveways
anyways to prevent a trip-hazzard and create proper rain drainage.