Yes, it applies to all spawns. Game speed also already effects the barbarian city creation.
Maybe I don't understand the concept of spawning then.

In the Marathon Fire games I have been trying to play, the barb cities spawn at an alarming rate. As I mentioned in another thread I took one out, moved away and another spawned in its place 3 turns later. This tends to happen a lot. Then, you are faced with taking out the barb city and moving the counter, or letting the barbs have a base for spawning other units. Also, a bit later, you can get the Red Dragon or the Four Horsemen in these barb cities near your borders.