Considering public institution are using taxpayers' money, I think all of them should be using open source software, for both budget reasons and in principle (to help grow the public open source community, and then benefit from it in the long term).

The problem here also sounds like somebody was trying to use Microsoft Office docs in an older version of Open Office. So they were the ones locking themselves in before, and now their solution for having hassle-free work is to reward Microsoft for it, and lock themselves back in? It's like a drug addict who thinks withdrawing is too painful, so might as well continue taking the drugs.