I would think that only Boeing, or the manufacturer of the recorder, can safely access it. I doubt that it has a USB jack that you can connect with a cable to any desktop PC and it immediately starts playback. As a bare minimum, the outer protective container must be opened - and they are made to survive in fire, or as this case may be, at the bottom of the ocean. You don't want to do this with a sledgehammer or a plasma cutter. You need drawings, documents, and special tools. Boeing has them. I doubt that the customer airline has them as well. It's not something they need to maintain from the inside - it's just a board with Flash chips. If it passes self-test, it's good to go. If it doesn't, back to the manufacturer it goes.
Unless the boxes have changed in the last few years they are actually wire recordings. Sounds silly in todays electronics world but the non-corrosive wire can withstand a lot of heat chips cannot and still contain data.
Actually it is the FAA or NTSB that can open up and transcribe the info.
We were able to get info off the Cockpit Voice Recorder as maintenance techs. They had a headphone jack for testing purposes. You have to be able to test them to make sure they work. No need to go back to Boeing as the safety agencies all have the ability to read the data.