Hi,
Remember that any recovery will be performed with a different ship, assets and crew. I would not expect anyone from the WHOI/GOMAR contingent to be aboard for Phase 5, unless it was for data interpretation, as a guide to the ROV operators.
The most important person to be aboard (exept the crew and eventual scientists) when black boxes are recovered is a representative of the french justice.
It must immediately put seals on the boxes when they deposit on board