It is private, that's why U-haul has to have a privacy notice telling you who they do and don't share the information with, and when they will and won't share it.

Sharing someone else's personal information with a random person without a subpoena or other court order would be a direct and deliberate violation of U-hauls own privacy policy, opening them up to civil liability.

U-haul is in fact already being sued for failing to adequately protect the private personal information of its customers.