This is your government on public sector unions. If the argument is, some functions are too critical to public safety to put in private hands, then that is an argument against allowing them to be unionized. If unionized, then the state no longer has a monopoly on the power exercised by that arm, which is the whole idea of putting it in the public sphere. So if you can't have private police forces running around, let's say, then it makes no sense to have the monopolized force of the state colonized or even dominated by a union with interests frequently opposed to those of the public.
NYC snow removal is just a vivid illustration of a problem that is about to blow up into a genuine fiscal crisis. Unions have held up states and cities for trillions of dollars in obligations that can't be paid off. Throw in the costs of an utterly failed public school system in many cities and you get an idea of the scope of folly of government by unions.
Further thoughts here.