The game would scale to an EV trained level 50. The mechanic where EVs apply after level up was retired in Black/White where they started to update after each battle instead, regardless of whether or not the Pokemon levelled up. Now, as of X/Y, any changes to EVs apply immediately -- that is, a level up or battle is not required for them to take effect. (More details on that in this post.)
So your Tapu Bulu will not only have its stats scaled to an EV trained level 50 -- its EVs should have already applied to its stats outside of the Battle Royale and Battle Tree as well.