The official Pokémon HeartGold and SoulSilver website has posted a news article stating that Ash's Pikachu will be distributed at participating Toys"R"Us locations in Canada.

Press Release

To celebrate Ash and Pikachu's incredible friendship and many future adventures, for a limited time you can visit Toys"R"Us stores in Canada to receive Ash's Pikachu in your Pokémon game. Ash's Pikachu knows moves such as Thunderbolt, Volt Tackle, and Iron Tail - just as it does on TV! Ash's Pikachu also comes holding a Light Ball, an item that doubles its Attack and Special Attack stats. This is one opportunity you won't want to miss!

Visit participating Toys"R"Us stores between February 9th and 20th to receive Ash's Pikachu. Remeber to bring your copy of Pokémon Diamond, Pearl, Platinum, HeartGold or SoulSilver Version (each sold separately) and your Nintendo DS system. Please note that you'll only be able to get Ash's Pikachu once per game.

Source: http://www.pokemongoldsilver.com/ca/#/news/ashspikachu/