Yeah, when I read this I thought "duh"; having an entire other team of developers come in and totally change a codebase and not communicate what/why they change

Yeah, when I read this I thought "duh"; having an entire other team of developers come in and totally change a codebase and not communicate what/why they changed to another team that's frequently working on that codebase sounds like a recipe for disaster. I can't imagine why anyone with even a small amount of development experience would think that would be a good idea.