It most likely is a cutscene. Considering Noble 6 is in passenger seat. And it would be kind of boring just sitting there with an AR, because you would do little damage to the Banshees, So i hope its a cut scene that way it will be more epic.
They need to come out with a better, longer trailer. This got me excited because i thought i was going to get a awesome trailer with loads of action, but what we got was just some (what looked like) cutscenes. PLEASE BUNGIE give us what we demand or else we're taking that giant slingshot. lol.
I would bet that something will happen from that cut scene and either you'll flip the hog or your gunner will get obliterated and somehow you'll either end up gunning or on the ground in this giant fight. Bungie has said that the AI driving mechanics are the best ever (where have we heard that and how many times?) So I would bet that they would want a part of the game that shows that off. Also, this cut scene could be the opening to Campaign level 9 that the Achievement states: "Complete level 9 of the campaign with the scorpion intact on legendary."
The scenery and lighting in this trailer really gets me pumped for Reach. It looks amazing, simply amazing!!