How have they worked for the last 10-15 years with Linux desktops if there are 800+ apps they need that are Windows only? They must have used both platforms interoperably, so why the need to switch to Windows only now? If management insist the whole network must run the same OS to simplify support / improve security, that doesn't bode well for an IOT / mobile app future.
Linux desktops reduce support and licencing costs for the common apps they run well. For more obscure apps that are only available for Windows, these should be virtualised (RDP-ed) where possible to avoid users needing multiple desktops or having to dual-boot. Further, if virtualised Windows VMs are isolated from the internet, they can maintain older versions and avoid paying for updates (reducing TCO). From the tax payer's perspective, all apps and data formats should ideally be platform neutral / open standards to avoid the long term costs of vendor lock-in.