> IT systems of European governments mostly run on Microsoft software and OS [...] that means that almost all of the data of European citizens — tax information, health records, etc. — along with security related data, are in proprietary file format...
> The problem with the proprietary file format is that Microsoft’s software is made to be incompatible with open source, which effectively forces all communicating departments within a government to use the company’s products, in order to ensure compatibility of files and ease of communication.
The operating system that runs on a system has no bearing on how the data for various applications is stored. As far as I know, Microsoft isn't providing the applications that store "tax information, health records, etc.", unless the governments are using Excel and Word to keep all that information rather than a database.
Even so, if they are using Excel/Word, the Office Open XML file formats are ISO/IEC standards, not proprietary.
There may be some problem of vendor lock-in here, but this article seems to have no idea what the real problem is.