This has only been tested on empty KotH servers and I have only done it 3 times but all 3 times there has been an increase in FPS and this includes when its day and the street lights are "off".
I have no experience with any map editor for Arma 3, otherwise I would try to remove ALL street lights from the entire map to easier be able to compare performance with/without them as the increase I have seen is fairly small and usually just 1-2 FPS, its not impossible its just a big coincidence but since so far its a 100% deal and the street lights I have disabled are few in number to get that increase, Im reporting this here on the off chance that the street lights are for some reason a drain on the servers(and what if all street lights all over Altis were having this effect?).