The whole synchronized music idea is really cool but here's what the practical logistics look like. Most mutant vehicles of any size have sound systems but are only significantly audible in their immediate area. In reality, the synchronized-sound thing could happen but no one would even know it, unless you also arranged to have the vehicles within a few hundred feet of each other. If you did that, the effect would be impressive! But hell, we try to arrange mutant vehicle gatherings and cruises almost every year, and they rarely happen because... shit just happens on the playa and plans sort of evaporate.
The only camps that are loud enough, and located perfectly, to make a dramatic effect are the large-scale 10 and 2 dance camps. Some MVs with sound located in between 10 and 2 as fillers would work well, but if they weren't within earshot of the 10 and 2 camps you wouldn't even know they were synced up. Effect = zero.
Wifi would be great for just a 10-and-2 sync-up because you could split the left and right stereo signals between the 10 and 2 installations for awesome effect on the playa. With just two (maybe three or four) camps to link, setting up the wifi would be easy and most importantly - likely to even happen.
Too much is not enough, and when in doubt double it.