Cool looking setup!
But I wonder why they didn't use fewer fixtures, and a higher wattage??

Well cause its cheap, because 12 400w fixtures make 4800w, and I think with 8 or 6 with 1000w, 6 make 6000w and eight make 8000w. So they went for 4800w. Since now they're starting to put LED on high mast poles, the wattage will be much lower, with 6 LED fixtures on the mast.

That logic makes no sense though. Higher wattages of HID are more efficient than lower wattages. 400W HPS is 50000 lumens (125 LPW) while 1000W HPS is 130000 lumens (130 LPW). Twelve 400W HPS lights put out 600,000 lumens. Using 1000W HPS, you'd need 4.6 fixtures (rounded up to five to give 650,000 lumens at 5000 watts. Twelve 400W HPS is 4800 watts. This does not account for ballast losses. Once ballast losses are accounted for, I think they would be similar in power consumption. The twelve 400W HPS in this case uses less energy but only on a technicality, because you can't have 4.6 1000W HPS lights. If you could, the 4.6 1000W lights would use 4600W instead of 4800W to give the same amount of light. 1000W fixtures are very expensive but I would think five 1000W fixtures would still be cheaper than 12 400W ones. 400W gives the benefit of more lamps though, so you won't loose maintained footcandles when a few lamps burn out. I guess it's all on how you look at it and who values what.