Yes. Members on a team are in a permanent alliance and start the game in communication with each other.

So is it just like the standard alliance you can get in the game?

So far it seems to be the same.

unlimited alliance, yes. I use that when I want some more challenge but not give them just more technolgies with the highest difficulty. It's useful, if you attack one of them, you are at war with all in some turns.

Ah, well that's not the same! Regular alliances are just max relations. They don't automatically follow war and peace.
Here's why it might be a problem. In Fallen Enchantress a team could have a strong and weak AI. The strong one would declare war and bring the weak one with it. Then the weak one, being weak, would beg for peace with the enemy, offering riches for mercy, and both would end the war, ruining the conquest plans of the strong teammate.