@Im OK
My guess is that part was actual game footage, what with the bars, numbers and what looked like damage indicators popping up when people we're hit... My guess is that the footage is edited to take things out of context to make things look more dynamic... it starts with a CGI entrance, moves into gameplay, and then ends with CGI... in the game you get the same thing but it doesn't flow as nicely; like lightning makes her entrance, then there is a series of battles, and then there is a cutscene that starts with Lightning finishes off the enemy and continues on with the story from there...

The question is how much does the player control during that bit of gameplay footage... does the player have some control over all the stuff going on there, or is something more like a limit break where it's kind of turn based and all the player does is start the move and let the game handle the rest... we have no way of knowing for sure... the later is more typical of final fantasy and it would be well within their means to make use of such dynamic camera angles while fighting, however the former would be quite awesome and is probably still possible for them to make... afterall, i think games like god of war, assassin's creed and so forth have shown you can to some nice cinematic fighting in real time (imagine Assassin's creed's dynamic kills, but being able to do them back to back or something =P)

So ya... it would be nice to see some gameplay footage without the cinematic trailer work... it is kind of a pain to wait for such things; i mean we had to wait this long just for an extended trailer, how long till we get some actual details!