The ETOPS enroute airports must meet the ETOPS planning minima at dispatch stage.
Once in flight, you can enter the ETOPS segment as long as the enroute airports are at or above your minima (not the more restrictive planning minima) and you have all the necessary equipment. Otherwise you have to reroute, fuel permitting, or make a stop.
Once inside de segment you can divert anywhere according to your minima, and in addition you can remain in the ETOPS segment even if you lose some ETOPS required equipment.
If all flights meet the ETOPS planning at the planning stage and the ETOPS airspace entering ones, statistically speaking, flying in such remote routes is a perfectly safe thing. If we didn't meet those, sooner or later something bad would happen.
Once in flight things are not so restrictive as they are at dispatch, and once in the ETOPS segment, you are the captain of your soul. There is no obligation to divert to the nominated enroute alternates, nor even to use the ETP as a decision point. You can decide anything, even flying for longer than the rule time, if required.
As a matter of fact, in some scenarios the ETP doesn't make any sense. Also consider that if you are flying a 120 rule ETOPS segment, you are considered to be safe as long as it doesn't take more than 2 hours. So if from the ETP to one alternate flight time is 70 min and to the other is 85 min, you are perfectly safe diverting to either one. Choose the one you like the best, never minding about ETOPS. Also it can happen that the ETP is in contradiction with another kind of decision point, like a terrain escape route. In that case, totally disregard the ETOPS thing. Respect the escape route, instead. If you met the ETOPS planning criteria and entered into airspace ETOPS meeting all requirements you are safe enough.
Hope it helps
Last edited by Microburst2002; 27th Jul 2014 at 11:46.
Reason: typos