Question

How much happiness do the Pokemon in the Battle Factory have?

Answer 1

I'm answering this because the previous answer is wrong.
As said here, a Pokémon with frustration will have minimum friendship and a Pokémon with return will have maximum friendship.
Hope I helped!

Comments

Source 2: experience

Answer 2

Well, the Happiness of the Pokemon in the Battle Factory will be the original 70, Because the Pokemon dont know you and you never trained them to their Lvs. The same goes for both Generations that contain the Battle Factory in them.

This means the move Return will not be as powerful as the move Frustration.