Another option: they shouldn't be government employees at all. It would be much better for them to work for the actual airports themselves and be certified by the government or a private testing organization instead.
There’s a lot of ATC that isn’t specific to a single airport. And lots of airports are owned by a government anyway.
LaGuardia, like many (most?) airports, is run by the government. This is a distinction without a difference, at least in this case.