I don't think there can be any real form of evacuation for humans if an event like this occurs. While humans have really advanced in terms of technology, I don't think we have what it takes to prevent an extinction-level event from occurring.
As far as I know, the highest we can only do is to predict the possible time of such an event and probably identify the possible direction of the impact before l it eventually happens. With our current advancement in technology, it does not look like there are places we can run to if an extinction-level event occurs.
For instance, what we have now are potentially habitable planets, meaning if anything should happen to the planet Earth, we might not be able to find comfort in other existing planets. However, humans are wise enough to identify any threat to Earth, we might be able to avert an ELE, probably in the future.