The scenery is based on data from Bing maps, but it's not just Bing maps.
I think there have been some comparisons between the Bing maps and FS2020 renditions of some of the locations in the screenshots released over the past few months, they show that the FS2020 scenery is enhanced over plain Bing maps.
Asobo are using various AI-based techniques to augment the basic mapping data, particularly where Bing doesn't have true 3D photogrammetry. They've made a big thing of this in some of the progress videos released a few months ago. I guess that's what makes this game such a poster child for Azure and the cloud in general, you take mind-boggling quantities of mapping data, then throw massive amounts of compute power and sophisticated ML algorithms at it to make it look "better".
I've flown around my own city, for which the Bing maps coverage is a bit sketchy. My house doesn't exactly look like my house, but it's in the right place and doesn't look wildly wrong.