The issue of handling legacy binary formats is one that impacts much more than old Word documents, especially for governments who have long-term archiving requirements.
I think governments should simply legislate “After 20 years, the documentation for all formats used in government data should be made public for access on government archival websites and is deemed unencumbered by IP considerations for the purposes of information retrieval of government data” as a matter of public policy. Hand them over or get a fine for obstruction or bad record keeping!
Of course, the regulations would need to say more than that to cope with industry churn and the ravages of time. For example, what if the vendor or product has been onsold and no-one knows where the documentation is now? What if the local sales body is no longer the sales body for that product, or the development organization is defunct. But that need not stop the general case.
Of course, for contemporary and future data, standard open formats are the thing.