In the mid-game of Civilization 6 you receive access to buildings like the factory or the zoo which have (in addition do some other bonuses) the attribute:
Bonus is extended to all cities within 6 tiles
Let's say city A has an industrial district which is at or closer than 6 tiles to city B and – similar – city B has an in industrial district close enough for city A. Will both Cities get the effect of one industrial zone*, or will both cities get the effect twice?
*Related question: I'm assuming "Bonus is extended" refers the all bonuses of the district. (The district itself plus all buildings inside, like the workshop) Is this correct?
Best Answer
EDIT: As of the Winter 2016 update, it seems it no longer works the same way. From the patchnotes:
Answer BEFORE Winter 2016 update:
First off, you can actually directly see the various bonuses by hovering over your city's production. (same for food, faith, science, etc.)
I found out that
A) The bonus does stack, a factory gives +3 production, a city with a factory of its own within range of another factory has +6 instead of +3, thus receiving the bonus.
EDIT : This bonus CAN stack multiple times:
As you can see here, my Capital is within range of 3 different fully upgraded Industrial districts, so it receives +9 from factory (+3 from each) and +12 from power plants (+4 from each).
B) Only the factory bonus was added to cities within 6 tiles, NOT the whole zone bonus. So say a city with no industrial district is in range of an industrial zone with a factory and a workshop, the other city will only receive the +3 bonus from the factory. Again, as you can see in the screenshot, my capital does not have an industrial district of its own, so it only receives bonuses from Factories and Power plants, not from the workshops.
This makes sense as the entertainment complex, for example, has multiple buildings that extend their bonuses. So each building is worth building, as each will only give off its own bonus.