Soren posted a message about Civ 4 in one of the Alpha Centauri forums. Since it might otherwise be overlooked, here it is:
Comment from Apolyton poster (edited):
Unfortunately, when bases are placed such that their radii overlap, tiles are assigned to one city or the other by the game, rather than allowing the player to assign such tiles himself.
Reply from Soren:
"you can switch tiles between cities by clicking on the tile in the city screen of the city you want to work it. This also allows you to use the governors but at a high-level determine which tiles should "belong" to which city (which wasn't possible in previous games)."
Here's a link to the entire post:
Comment from Apolyton poster (edited):
Unfortunately, when bases are placed such that their radii overlap, tiles are assigned to one city or the other by the game, rather than allowing the player to assign such tiles himself.
Reply from Soren:
"you can switch tiles between cities by clicking on the tile in the city screen of the city you want to work it. This also allows you to use the governors but at a high-level determine which tiles should "belong" to which city (which wasn't possible in previous games)."
Here's a link to the entire post: