If this scenario was planned and prepared for there still would likely have not been perfect knowledge- but I would expect far better than what the response was.
I would expect there to be confusion or not perfect knowledge if there was no planning and preparation for something like this.
I guess I have a hard time believing that Vegas of all places does not have their ducks in a row when something like this happens. It is always on the list of likely terrorist targets and has been since 9/11.
I would suggest your definition of ducks in a row is imperfect at best