Cards that have been removed from the game by the hideaway ability of one of the Hideaway lands form Lorwyn (for example, Windbrisk Heights) do end up getting played when their non-mana activated abilities resolve. This means that abilities that trigger when a spell is played will trigger. If Emrakul, the Aeons Torn was removed from play by a Hideaway land, its ability that grants an additional turn will trigger as you do end up casting it.