I'm getting a headache too from all of this. I only know one teensy, tiny part that I can answer, and I don't know if you'll find it helpful or not. You said, "They were founded at the same time." That cannot happen. Why? Well, even if they were both founded on the same in-between turn, the AI takes their turns in a certain order. (I want to say it's in the same order as they're listed on the F8 Victory Screen, but I'm not certain of that.) Whichever AI's turn comes first, their city would have priority. Now that I've muddled the issue even more, maybe someone else knows the answer to the rest of your question about cities A, B and C.