Same as Doca, I am sure that the trailer only consists of rendered videos and not of ingame footage.
So we can't tell what they did besides the trailer, which is - as already said - really nice.
Let's wait for the first screenshots! After we got an impression of the mod itself we will be able to discuss whether they had to do something on source-code-level or not and how they propably did it.
Take a look at FO - they didn't change the source code and you wouldn't guess its Armada 2 FO is based on.
