Yeah sure looked to me they were aware the moose were there. Looked to me they seen a opportunity to film something cool. So set up a guy filming, then it’s let’s go terrorize the natives.
The way I understood it is that the camera person was videoing the moose and calf, but not associated with the snowboarder, which is why he was yelling "heads up"
I've stopped to take photos or videos of wildlife from a safe distance, so I could see it happening this way.
For sure, I don't think its cool to mess with wildlife.
Edit: I watched it again and it looks like the first snowboarder was somewhat close to the moose but those who followed took a much different line, well above the line. I'm pretty sure the snowboarders in the video were surprised by the moose and the guy filming was an innocent dude who was taking a video of the moose and shouted "heads up" when he realized that the snowboarders were about to infringe on the moose nesting in the trail. Also note how deep the snow is where the moose sinks in while trying to charge the boarder.