There was an Event in Japan that let people get Speed Boost Torchics in the Dream World in Japan. They could have been traded via GTS negotiations.
Pokesav, PokeGTS, Action Replay, or PokeGen.
Pokegen or Pokesav so in other words they hack
They probably used AR to hack the game or Pokegen/Pokegts. Also if I recall correctly there was a special event in Japan when B/W was first released, but I could be wrong about that.