Well, the city would have had to have given them special permission to do that.
I don't think they would have done that on a cloudy, foggy, rainy day.
Air traffic doesn't usually (ever) fly 500 - 600 feet above the downtown core. By the time you notice the beacon it would be too late
It will be a different story once we finally get our 1000+ foot supertalls! *dare to dream*