I did not get a reward for completing the event, by waiting in the zone until the race timer finished (and completing the race before the timer expires, of course).
I did get it in Gendarran earlier, just like every other non-beetle style race offers, as they are events.
Update: I also got the event reward in Mount Maelstrom (besides the daily). Just no event reward for Brisban.
Update 2: For what it's worth, ran Brisban again today and waited and no event reward. So far all the other races give you an event reward.
Solved: I waited for the timer to count down, and there is an event reward, there's just no chest (for whatever reason) in that zone.
In the event I don't get a chance, thank you all for the company and help when I needed it from time to time.