Who is the winner with alliances ?

Are SP of each alliance member cumulated ?

You get the sp you earned + the sp in the sp pool divided amongst each ally. So if you are looking for more sp, it's better to fight everyone since you get that sp pool all for your self if you win.

Ok, but who is the winner in that casual game (Atlas 50K - 5 country start) ?

Alliance B - SwampNewts: 2144 SP (3347 armies for 79 countries and 162 cities)
Alliance A - Baalhammon: 1567 SP (2697 armies for 200 countries and 342 cities)
Alliance A&B - Lord of Chaos: 699 SP (225 armies for 25 countries and 44 cities)
Alliance A - Dah: 671 SP (512 armies for 70 countries and 119 cities)
Alliance B - Professor_Chaos: 277 SP (1884 armies for 99 countries and 155 cities)
Alliance B - Rambini: 231 SP (632 armies for 53 countries and 81 cities)

If you sum the SP, Alliance A is the winner.
If only first position matters, Alliance B is the winner.

And what about crossed alliances ? In the example, Lord of Chaos is allied with A and B.

If the game is decided by sp, only swampnewts will win since he has the highest sp. His allies all lose.