Is it the same as on the H4D 1/800?
Hasselblad H system flash syncs at all flash speeds the fastest being 1/800.
You can do all the high speed sync things the Phase One DF and LS lenses can do, but just one stop slower.
A 1 stop ND filter and more flash power and you can get the same sun control.
There are some very good examples of the Hasselblad High Speed sync capabilities in a previous thread:http://www.luminous-landscape.com/forum/index.php?topic=71679.20
See the posting by Brendan.