I would say that the diplomacy of this aspect is a thousand times deeper than the gameplay and strategic elements. Those are (for the most part) straight-forward and, yes, there are some clever things that can be done, but it shouldn't be too difficult to more-or less master that part of the game. But the diplomatic relations that go on... Those are infinitely more complex and mysterious

Every game I play is a new experience and a new adventure into the unknown. Even when I've had a strong ally for the entire game, very dependable, a "bosom buddy" or whatever you want to call it, there still sometimes comes a twinge of concern near the end... "Will they get greedy and stab me in the back for that #1 spot? Why does he have so many drills right there?" etc
I think some things are generally true though:
1. The 4 hours of time before the game allows the first launches are actually a critical time for the game.
It is a very important time to communicate with those around you and tentatively start to create relationships, understandings, plans, etc. You can't ally with someon that you never talk to, and I think (just a guess on my part) that your chances of having a true ally diminish with time as they may already ally themselves with others as time goes on.
2. Courtesy and diplomacy will trump a snatch-and-grab style.
I'm not the most experienced player in the game but I think, after the games I have played and also talking with others, that this is true. Let me illustrate:
Recent game I had, there was a patch between me and pink above me of 4 factories tightly clustered together and all 4 of them had double shields. It was a highly strategic and powerful spot. Pink and I were about equidistant from it but my arrangement was slightly advantageous to his. I tried to talk to pink to arrange a peaceful opening but it seemed that he didn't reply. I felt snubbed and decided that I was going to slam him, hard. I felt 90% confident that, with the right opening, I could end up with all 4 factories and then I would probably be able to crush him. I even talked to 2 others about how pink had snubbed me, I was going to crush him, and who was with me? They were with me. So the game started and I had my aggressive opening. Right at this time, subs already launched, pink opens dialogue and with some simple and frank diplomacy he talked me down and we arranged a peaceful opening. We went on to be great allies and dominated the game. It is about to close in 24 hours with us as the top 2 players.
Could I have crushed pink at the opening? I'm pretty sure, but that would have set off a chain of diplomatic dynamics that are difficult to predict.