Those planes probably have 3 or 4 engines. For 2 engine cross ocean flights there are definitely rules about distance from a landing option.
Often that's how OEM's will get their cold weather testing done, by just flying up in the winter.
And here’s a list of diversion airports: https://en.m.wikipedia.org/wiki/Diversion_airport
They hardly do anymore. The remaining 3 and 4 engine airliners like the 747 and A380 are on the way out. Twin engines like the 777, 787, and the A350 are going to be the only planes flying these long haul routes going forward because they are just so much more efficient. With increased reliability over the years, ETOPS regulations have loosened up far enough that you can fly to/from any point on earth without being beyond the max range from land.