A good taxi driver will recognize that if there is a major event in an hour, it's better to avoid some routes, even though Google maps might still be showing them as perfectly clear. They won't be in 30 minutes.

Not really, I live about an hour outside of the city and carpool in everyday. I can tell you first hand that Google is always late in recognizing traffic pattern changes. It's actually become a bit of a joke amongst our car pool because we get the alert once we're already stuck in traffic.