Infinite City Spam (ICS) has been the go-to Win Button in the Civilization series for some time. In short, the idea is to build as many cities as humanly possible; even if some of those cities aren't much good, they're still better than not having the city. In Civ I, II, and III, there wasn't any reason not to build a hundred cities as quickly as possible. Civ IV introduced a per-city "tax", which increased with the number of cities in your empire; this stopped ICS, because a low-value city would damage your empire.
Civ V tried to prevent ICS via the Global Happiness mechanic. The idea was to make it harder to build extra cities by adding a per-city penalty to Global Happiness. Unfortunately, Civ V also has a goodly collection of per-city bonuses, making ICS workable again; it's telling that the answer to "How do I beat Civ5 on deity?" is Infinite City Spam. (Per-city bonuses include Martitime City-States and a wide variety of social policies.) Clever players found ways to do ICS despite the Global Happiness mechanic (mostly via the happiness-producing buildings).
Civ V has had several patches and expansions since its initial release, in an attempt to reduce the efficiency of ICS:
- Maritime City-State allies only give +1 food per city, not +2.
- Happiness buildings now produce Local Happiness, which cannot be used outside of the city that produces it. Tiny cities with all of the happiness-producing buildings no longer create a net-positive-happiness city (unless there are luxury resources or world wonders there, which are limited in supply).
- Happiness buildings produce less Happiness. (Typically +2 instead of +3.)
- The Social Policies have been overhauled; several of them no longer give per-city bonuses, or delay those bonuses until all 6 policies in a tree have been filled (to make it harder to accumulate a large number of these bonuses).
- Research costs now increase 5% per city (including puppets), and Libraries no longer have specialist slots; small cities will be a net penalty to Science production.
- Gold production was overhauled in Brave New World, reducing the power of improvements like Market and Bank while granting limited-number-per-civilization Trade Routes.
So, given the above changes, is Infinite City Spam still a good strategy as of the Brave New World expansion, in games on Immortal or Deity? Is it still viable, but now much weaker? If it's still possible, how is it done? (I'm assuming the guides from 2010 are obsolete.)