The CVR may provide important exculpatory evidence for the flight deck crew. And whether the contents are exculpatory or not it would almost certainly have to be produced in any case as part of discovery proceedings. If it still exists of course...
I do not believe that purely civil tort cases may assume the the CVR has to be produced .
It was designed and installed as a regulatory requirement to serve a specific purpose. To extend that purpose should necessarily require cooperation by the FAA and I doubt that they will accede.
I also don't believe that United can control it's custody either.
The best thing that can happen here is for the CVR to be bulked erased and re-installed for continued use since no restrictions are placed against its reuse by the Feds.
I can't help but think that any court actions (to be filed) would not include the operator of the flight nor it's equipment.