If the person steam sharing LoP with me buys Overture, can I be 100% ill get it too?

So say my buddy doesnt care about overture but he shared the main game with me on steam. I cant buy overture straight up because id have to buy LoP on my own account first. If I pay him to buy it on his account, thats sharing with mine through steam family, can anyone tell me with certainty it will allow me to play?