This doesn’t seem like a hard case at all. The answer to my mind is that incidental use must be fair use otherwise pretty much every photo taken anywhere but a wildlife preserve is in violation of somebody’s copyright or trademark - it’s just a subset of right of panorama, which we don’t explicitly have in so many words, but mostly do in the US. Think about all the copyrighted, trademarked and design patented items that appear in every photo you take, even down to tattoos. In a world where almost everything you make is automatically copyrighted, almost every photo you take includes items copyrighted by somebody else.
The copyright maximalism proposed by the mural artists would make most photos into infringement - the artists don’t seem to realize that their own freedom to create is based on the flexibility of fair use.
The additional claim under the “Architectural Works Copyright Protection Act” is interesting, but I think it will be unavailing.
