The timing always did look a bit suspicious. They managed to get the Ocean Shield in location just in time to hear the last signals from the pincers. Well away from the location of the previous aerial search area.
I suspect it is very likely some other data was made available to allow this to happen. The nature of this may never be released. It could be a satellite, or could be JORN.
Somewhere about a few hundred pages ago, there was mention of a British? submarine with very sensitive equipment that would be able to 'hear' the pingers at some distance. This was just before Ocean Shield made its way to the search area location. The submarine was recalled at about the same time as Ocean Shield moved in. Of course for security reasons the position or positions of the submarine were never made public.