https://www.gamespot.com/articles/all-pokemon-go-eggs-will-produce-generation-3-poke/1100-6456310/

This week, developer Niantic added a new set of Pokemon to Pokemon Go, all from Generation 3's Hoenn region. Recently, the studio also revealed that, for a limited time, any egg you find will hatch a Pokemon from Hoenn.

This means that there's another way to grab Hoenn Pokemon that doesn't involve stumbling across them by chance. Niantic announced the news on Twitter alongside a video of an egg hatching into Torchic, one of the starting Pokemon from Ruby and Sapphire.