No, it doesn't learn it. Smeargle only learns the move if it uses Sketch directly after the opponent uses the move.
Ex: Chikorita uses Razor Leaf, Smeargle uses Sketch, Smeargle learns Razoe Leaf!
But be careful, as if you fill your moves you're have to waste Heart Scales remembering and deleting.
And it can learn any move, sig or not.
source: My Knowledge.