Bringing the Thunder
I don't believe so. I think you have to trade to see the evolutionary line of the third starter that neither you nor your rival picked. ):
Only the first Pokemon in that form.
Also, you need to trade for Buneary/Skitty and Vullaby/Rufflet, both of which only appear as wild Pokemon in the other version and remain absent from the trainer rosters. And probably Reshiram and Zekrom as well. Aside from the dragons, though, as long as you have access to the GTS, you'll be fine.