It's actually quite a small number over the size of the public service. Public servants are no different from all Canadians. They still have to go out for essential reasons and take care of their essential business. They still have to care for others who are sick. They have kids in school who are sometimes bringing COVID home from school. Families who work as health care workers are bringing it home.
The majority of the cases are not transmitted in the workplace, but it is nonetheless reported as being a public servant who got COVID.