[mordae]

That's nonsense. Most of the software in question was written to support the administration. There is no existing closed source nor open source software as such, only software ordered by public sector and delivered by private sector under a license that guarantees vendor lock-in. Which, obviously, is insane policy and must go.

The software is updated to contemporary standards and rewritten as people come and go about every 10-20 years. Mandating it to be open source makes it simpler for new vendor to take over in those 10 years. And it might provide other benefits such as some degree of code reuse.

As for the foundational software, there usually is a regional partner of Canonical, SUSE, Red Hat, Microsoft and so on who re-sells the licenses and provides part of the support.