Only the instance that does the actual publishing get's this event. All other instances will get a notification to remove the page from the cache to be able to reload it's data from the database. If all instances would get the event, you would have a much more complex logic if you for instance want to synchronize something with another system since there will be lots of simultaneous events.
I am deploying to production which is the sole load-balanced environment. I have an issue with regard to a Delayed-Published page in this environment. If I subscribe to this event, do all nodes in the pool recieve this event? Or does only one?