Let's say that you battle a Tyranitar. The wild tyranitar beated 5 of your 6 Pokemon. Will the Tyranitar have the EVs for those Pokemon? If you catch it
No it wont get EV's because you need to get exp from the opponent to get EV's. Source: http://pokemondb.net/pokebase/108638/you-gain-youre-battling-wild-pokemon-and-kills-your-pokemon (I already asked this question :p)
No it won't. Just like how the wild Pokemon doesn't level-up when it has just defeated a level 100 Pokemon. But if the Pokemon is able to beat 5 of your 6 Pokemon, it probably has good EVs