`Area.spaces[0].region_quadview` of a View3D has no members for every of the four views, but refers directly to the right bottom view. All other 3 seem inaccessible. Or am I overlooking something?
There are several WINDOW regions in quadview mode, but there's no way to get the region (space?) data from it in python.
It's pretty arbitrary to have the bottom right one adjustable, 'cause the TOP right one is the one you would normally navigate.