I worked in a Singapore government agency for 4 years, and though I only knew a little about UX back then, I was involved in the building of internal systems. Resistance to change is real and tough. This is because the government employees regard their work as important in real time, and many times, it is. They would rather stick to old and less efficient ways, as they can't afford to take the risk of messing up their work temporarily while learning about the new way of doing things.
Based on my experience, there are several strategies to get user buy-in for a new system in such an environment:
1) Show evidence that the new system will actually improve their work efficiency and/or effectiveness, either by statistics from user tests or giving examples of where it has worked for other agencies.
2) Ease their transition into the new system, providing intermediate steps to transit from the old to the new so that it's not a one-time big change, and assure them that there is a fail-safe to fall back to the old system if the new system doesn't work.
3) Get the managers'/decision makers' buy-in. They are usually more forward-looking, and if you can prove the usefulness of new systems and processes to them, they can convince/enforce their employees to adopt it.