Presently, eggs can evolved before hatched, using a glitch.
In that sense, almost every Pokémon that can breed in those games, can be obtained at lv 1, barring stone evolutions.
(tho some stone evolutions can be obtained at lv 1 natively anyway)
Additionally, those mons can be traded online. Presumably they allowed lv 1 evolutions to be traded, because eventually Pokémon GO support (via HOME) will be added.