Saw this on the WAYWO thread :) Really nice job. The Marmoset renders and the high-poly are awesome. Was there any ZBrush involved or was it strictly polygonal modeling and floaters?
I usually use a combination of "make live" "append to polygon tool" and "transfer attributes" (for vertex positions). Not the speediest maybe, but all native Maya.
The textures are blended by vertex-colors on the terrain mesh. The white lines for the parking-lots are usally decals. Decals are polygon-meshes that are on top of the actual geometry.