Were the matter to go to court, depending on the full facts, the neighboring property may be able to establish an easement. See, e.g., Diener v. Ratterree, 57 Ark. App. 314, 945 S.W.2d 406 (1997). The electrical utility, though, is not going to litigate that for the neighboring home, and I'm also skeptical that they would want to branch the neighboring property off of your water line (which is presumably sized for a single home) unless it was difficult to impossible to run an independent water line for that home.

