Boeing764 From Canada, joined Apr 2001, 298 posts, RR: 0
Reply 1, posted (13 years 4 days 14 hours ago) and read 1219 times:
The oceanic tracks are seperated by, I think, fifty nautical miles horizontally. So when an aircraft needs to divert they call the controller on the HF radio and advise him/her of their situation. There is lots of room between the tracks to turn right or left and descend to an altitude they are able to mantain or an available altitude for an opposite direction routing. The controller can maintain seperation between all flights via voice communications or Satcomm.
I am no expert but I used to listen to San Francisco ATC on my shortwave radio.