I think it's 720p with post-AA.
Looks like 720p 2xAA, but this shot looks like it might be temporal 2xAA. A number of edges in other shots look like they have a post-process AA as well. Perhaps it's something similar to SMAA T2x. *shrug*
"You keep using that word. I do not think it means what you think it means."
Never scale-up, never sub-render!