I wonder if data centers will have to start doubling as automobile junkyards to conceal themselves.

While probably not a state agent, I've personally done online interviews with some people that were clearly lying about everything and trying to feel out details about the company. People claiming to live in our country and being citizens but having little ability with the language, saying they would love to come to our city but it's a bit far, saying they graduated from a major university but being unable to describe anything about the town (with their resume mentioning graduating from a different university, and their LinkedIn a different university from either), random people moving around and arguing in the background, all their work was with random crypto businesses that shut down within months. I had to stop my coworkers from saying too much. I had to convince them why hiring that person for remote work and giving them access to our servers was a bad idea. There are without a doubt companies giving similar people physical access to their hardware. And there are undoubtedly people who practice interviewing to better deceive companies.

Building a fully camouflaged datacenter could be done at much greater cost, but you still can't hide its thermal emissions from infrared. Basically every watt hour used in a datacenter environment turns into waste heat ultimately rejected into the atmosphere (except for the 0.000000001% that leaves the facility as photons down a fiber), so if you have N megawatts of waste heat from a rectangular shaped building located on a 300 x 400 meter sized plot of land, it's going to stand out.