Pretty sure those are actual people talking, it not in game narrative.It certainly looks interesting, but damn, is that fake narrative cringeworthy.
It seems to be a running theme for these carefully orchestrated "gameplay" trailers, you can see the same thing in the first big Titanfall showpiece. There the voice over of the "players" was so abysmal that they had to re-do it when they released it online.
I hope this fad either dies out or the developers are able to fake it better, because it's grating and distracts from what might otherwise be a pretty nifty trailer.