Nah, it's not working.
This time there's no stones next to the river, but there is deers, so I'm using a camp.
City plot = 2/1/1. Unimproved deer = 2/1/1. Both next to same river. City net = 4/5/5.
Now add river on the other side of the already rivered deer. No change.
Now remove river which we just added. No change.
Now build camp on the deer. Deer becomes 2/2/1. City net = 3/7/4. Should be 4/6/5!
Now try adding river on the other side of the deer. No change to plot. City net is still 3/7/4.
Now remove the river we just added. City net still 3/7/4.
Add the river back again. City net 3/7/4. Remove river, 3/7/4.
Further tempering with rivers around the deer plot (leaving the original river untouched) show no change.
So instead of 4/6/5 that we should have, we have now 3/7/4.
Tempering with rivers gave no change whatsoever.
The following is what I've been able to gather as consistently reproducible results.
1) By unemploying the only pop, the Food/Production numbers don't match the city plot numbers.
2) Food numbers always decrease each time, production numbers always increase.
3) It happens with a worked tile, and upon modification of improvements.
Wierrrrrrd
EDIT: Oh and I'd rather sit on this version than to have IGE become unwieldy. There's got to be an explanation to this, just have to test it the right way to find out, I suppose.
EDIT2: I tried using the official SDK's Live Tuner to repeat this experiment, but everything works as they should here. It seems that IGE is doing things different to the Tuner. Perhaps there's like a "safe" function call somewhere that the tuner is using. I don't know, just throwing out ideas.