You know, I suspected a 3d tool was used in the latest CC game, but I wasn't 100% sure. The maps really are the nicest ones so far. That's great news that the CC3 maps are not limited by colors. I was afraid it was like SP or something with a limited color palette. I'd love to see what you have regarding CC assets!
I see huge advantages to making a map a purely 3d render:
The lighting can be quickly and easily adjusted. Hell, why not just use an HDRI image to light the whole scene? With the right tone mapping and linear light info for adjustments in 32 bits you can make it look just like a photo of a miniature battle set. I mean it literally can look like that. You could split the render passes for shadows, roofs, trees, whatever . . . and have total control of everything. The maps could look so good the vehicles and men would look totally out of place!
Elevations with real height info, so no painting hills, but real hills.
It could be truly a perspective map and not orthographic. A purely orthographic view feels less real, in my opinion. If you put a perspective camera high enough in the air and use a powerful enough zoom lens, then it works. Trying to paint a realistic perspective map (and getting the shading correct) in Photoshop is just too damn hard.
CC3 is my favorite. I would love to repaint the default maps. I think that if someone really wanted to learn 3d: modeling, texturing, lighting, and compositing, then having a project of remaking the CC3 stock maps would be an excellent exercise. It doesn't matter if CC3 is an old game, because what is learned in the process is useful in any other contemporary project, and along the way remake a classic game that would be a pleasure to play on.
Indeed, someone could learn all the relevant contemporary concepts about 3d artwork while remaking something interesting like CC maps, instead of slogging through tutorials about making bedroom furniture scenes just to get relevant information. (Yes, check out the Blender community making countless renders of bedroom scenes! They are so boring is hurts, but if you want to learn photo-realism, then bedrooms are the thing to learn.)
All I did here is exchange the light texture: a single HDRI file changes the lighting. The tone of the map totally changes and the shading adjusts automatically. It is extremely simple. The last image shows how easy it is to separate the roofs and trees.