I expect that part of what I'm talking about is tacit knowledge, but I bet that some of it is explicit but localized knowledge. The knowledge (whether tacit or explicit) remains local partly because no one is interested in hearing about it-- too arcane for the lay public, too low status for scientists, partly because a lot of it is trade secrets and/or requires a security clearance, and partly because it's highly specific, which means it gets forgotten if a project or technology is abandoned.