If no other tone=mapping was done, it must have been done in the stitcher.
I think of tone-mapping as "local contrast enhancement" (and perhaps local color saturation enhancement). This image was made from 480 images, so it may be 48 x 100 images in size. Look at the size of each of the cloudy lights and compare to what you guess the size of each source image is.
The OP claims to have used f/8 at 1/160, but some areas of the sky are darker than other areas. There are few shadows and no clue as to where the sun is. IMO, the big clue is the halo around the building and other things -- the sky doesn't change color like that, especially not in square chunks.
I think somewhere in the OPs workflow, some luminance adjustment was done. It may have been done by the stitcher, but my first guess was that the photographer used an auto mode.
The OP claims to have used a Canon S5. And there is a lot of dynamic range in the image. I don't think the 14 bits of range you get with a 1DMIII could have captured this scene, let alone a P&S like the S5.
This image is a 16 column x 30 row section of a 30 column x 40 row image.
FYI, I waited until the sun moved behind another building (to the left-west-as you view the image), so the lighting was fairly uniform in the lower part of the building. Since it took over 1 hour to take the individual frames for this image, clouds did move.
I will repeat, I made no modifications to the image pre or post processing. Exposure settings were manual, focus auto. What you are most likely seeing is the result of blending between the overlap of successive frames where the intensity of the reflection changes with the angle of incidence, and with the movement of clouds. Another factor is the many different angles/layers of the glass on the building, which will have a large effect on how the light is reflected/refracted, and the depth to which one can see THROUGH the reflections to the inside of the building.
While the Canon S5 does have its limitations, I have been most pleased with it so far.
for more examples of gigapans taken with the S5 and also the Olympus E-510.
Aloha from the middle of the Pacific Ocean,