no contract can trump the fact that things and people that are visible from public property have no expectation of privacy.
Correct. Also, no contract not agreed to by the party in question can surrender any of their rights.
For example: your next door neighbor whose backyard is visible from your property or the public street cannot sign a contract with a photographer for exclusive landscaping rights and then take away your right to photograph the portion of their property that is visible from the street or visible from your property.
They can sign an "exclusive" agreement, but it's not worth the paper it's printed on, unless they conduct physical actions on their own such as installing high fences to protect the exclusivity.
You retain those rights, and so long as you do not commit a grievous breach of privacy: such as trespassing onto their property to open a gate or create a hole in a fence or covering, or conduct an intrusion upon seclusion such as photographing your neighbor naked in their backyard behind a high fence, from your ladder (It's not a breach if you use a taller tripod or climb a ladder on your property or public property to get an aerial view of their lawn, not photographing anything offensive or invasive to their person): there is no legal authority against you as a 3rd party to stop or prevent you from photographing just to support their obligations under an exclusivity contract.