A *properly run* government office will use the work from home days and other perks that are not in the union contract as incentives to keep employees working at a decent pace. If they have to re-apply for those perks every quarter, and poor performance means denial, people won't slack.
Some places will use desk locations and shift hours as other motivators... to find the competent employees, look for the ones with a desk by the window or who's hours begin before 8.
I recall one small agency had an entire floor where they sent all of the problem employees, assigned to do only unrewarding repetitive work. Work that provided no useful or transferable experience. Bad managers were sent there to manage the bad employees. They even had a few nicknames for the floor, names that when spoken would immediately get a slacker back to work.
Bottom line: creativity is required on management's part but as long as there is wiggle room, what happened at the USPTO can be prevented without any drastic changes to the actual rules.