Can visitors speed up egg hatching?

The practical effect is that your friends list is part of your hatching setup. Eggs go into incubators, and an incubator turns an egg into an Aniimo you can actually put on a team roster. Until that timer finishes, the egg is not a creature and cannot do anything for you. Anyone who drops into your base can take a piece of that wait off.

So there are two things to do with it. Keep eggs in incubators rather than sitting on them, because an empty incubator gains nothing from a visitor walking past it. And visit other people's bases, since the same help flows the other way.

You will have eggs to feed this. Logging in across multiple days rewards a random perfect egg, which is exactly the kind of thing you want in an incubator early rather than saved for later. Note that the Aniimo Eggs in Egg Heist are a different job. There you are carrying an egg to an escape boat as a match objective, not incubating it at home.

Not settled: How much time a visitor removes, and whether there is a cap on how many visitors can help a single egg, is not settled yet.