GKplan and others - I am basing my questions on the facts included in the interim report which many people seem not to have bothered to read before they post here.
If the IAAB have got their facts wrong then discuss the GPWS boundaries but I suspect it is unlikely that they have.
Rivet - I expect there is a permission in their AOC to operate IMC below MSA over water.
Agree Crab that some appear not to have read the report. Just trying to clarify that the note 15 in the report refers to mode 4b which is entirely predicated on rad alt and is a height boundary not a forward boundary. This is a basic GPWS mode that does not look forward, only down. The only relevance of airspeed is as a switch to change the height at which a warning will sound and also the actual warning sounded.