If you want to dig more, I suspect Microsoft got a lot (if not all) of it from blackshark.ai . They're one of the companies whose logo shows up during game start.

I knew their name because, when I worked for an Airbus subsidiary, we talked with them about a solution to generate 3D environments for any/every airport.

They had some cool stuff but also some wonky stuff at the time (like highway overpasses actually being rendered as walls across the highway).