Normally they have english announcers and just a few shows are acctually translations since this is the NHK World service most of the shows are originated in english. These days they are parsing a lot of feeds or TV coverage from local japanesse TV stations from the tsunami striken area therefore the need of translating all that material instead of creating new english only content specially for NHK World. Normal news shows are still broadcast as before with english announcers but the rest of the time they have to fill the old regular programming with this disaster-related local content and translate it on the fly. Kudos for them in my opinion for keeping their audience updated as best as they possibly can.
I do not remember that CNN was distributed in the clear or open for anyone to be able to keep updated about the Katrina hurricane situation not only via its main feed via satellite but also via its vast network of cable and satellite distribution network, please someone correct me if I am wrong, but at least with the canadian operators CNN kept being a premium service not included in the basic package therefore if you were not subscribed to it you were not able to follow its 24h coverage. In the case of this disaster in Japan , NHK has not only opened its normally encrypted premium service, NHK Premium, but also has authorized the pay tv providers to open its signal on their services , heck even the greedy Canadian Rogers TV has it open for all its digital customers to watch it.