In my latest Science Victory, I built a huge number of Industrial Zone Projects, ranging between 2 and 4 turns each, due to spamming Industrial Zones and Power Plants to almost every city (I had about 30 or more cities). I was getting 128 Great Engineer points per turn and I'm not sure IZ projects are counted in this rate either, since they are lump sum added when the project ends.
I can say that I was getting a Great Engineer every 5-10 turns, mainly because of the Industrial Zone Projects. It seemed even more frequent, since I was getting huge numbers of Great Scientists and Great Merchants too. Almost every city had a Commercial District and I built no Commercial District Projects, only a handful of Campuses and every such city built Campus Projects too. Yet, I had more Great Scientists than Great Merchants, so the Campus Projects must have been very effective in generating Great Scientists points.