If anyone, it's the companies interfacing them that will have to bear those "interoperability" costs. At least until they also switch to LibreOffice or something compatible enough. IMHO this is much better than them requiring Office-formatted documents.
Letting the administration be the pioneer in this front is sensible both morally and practically. Morally because the administration should be pushing for the greater good for all citizens, and practically because people/companies can not just "choose another provider and sidestep the issue".
Once nearly everyone is forced to have processes in place to interface with the administration using open standard formats, small companies looking to do business will have a much easier time asking for these formats too.
I can only imagine the headaches they are about to incur with this switch.