In the wild, well, obviously not, but I know how to battle the ones from Kanto in SS that belong to NPC's but not the last Johto or Hoenn or Sinnoh Starters.
Bulbasaur/Ivysaur/Venasaur: Route 28 Ace Trainer (Female near Tohjo Falls)
Charmeleon/Wartortle: Ace on Route 15, I think
Charizard: Champion Lance
If anyone remembers more, comment and I will edit. (No, not you, Bluedevil, since you are the one who doesn't know.)