There are several reasons and one is that it almost was designed to fail
It was bureaucratically planed so only the migration to FOSS was planed but nothing was done with the document standards.
So they decided to keep an M$'s office suite from 2000 and to combine it with OpenOffice. Even if Microsoft simply has ignored ISO standards and made their own, they are not the ones that get blamed when a Microsft Office document does not open correctly in OpenOffice.
Old Microsoft macros were kept and when they did not work on OO it was a token of the lacking ability of open source. So yes - this was designed to fail.
keeping M$'s old office suite around guarantees nothing works with anything else. No PDFs, etc.
Since most people are conservative it is almost an instinct to defend the known:
They did put some effort into a lengthy analysis, but it's comparing apples to oranges all over the place and not accounting properly for the costs of that other OS and its office suite.
One blogger put it like this:
It's as if some 'higher-up' commanded that a hefty report be written to justify the unjustifiable. I have no clue why that energy would be wasted when Munich is announcing success and documenting what it had learned in the process
So it boils down to that they really did not want to change anything. And who cares?
It is only the taxpayers money anyway.....