Well with Alain's godly overpowered Mega Charizard X, there is just no way that Paul doesn't get slaughtered 6-0 even with his best team. Considering how invincible E4 members are depicted in the anime, to even beat a top calibre E4 ace level Pokemon Paul would have get out the best combined efforts of his Pokemon with his best team. And imagine if that E4 ace Mega Evolves, and gets twice as much stronger with the ME boost, Paul has no chance of taking it down even with his best team in a combined effort.
And MCX defeated a E4 Mega Evolved ace Pokemon that is Malva's Mega Houndoom, even after being exhausted and weared down by battling 9 Mega Evolved Pokemon before. That says enough.
With MCX, unless Paul puts to good effect some subtle status moves and their effects, he gets swept without MCX losing barely any health.
Without Mega Evolution, it'd be a better matchup:
Tyranitar vs Drapion: Drapion sets up Toxic Spikes and recalled
Tyranitar vs Froslass: Froslass (win after a very close fight with all the weather effects like Sand Steam and Hail into play, I assume Froslass closely pulls off the win due to Snow Cloak evasion)
*Seeing Toxic Spikes being set, Alain sends out Unfezant to avoid it*
Unfezant vs Froslass: Unfezant (should be an easy revenge KO, if Froslass uses its evasion tactics well it might get some damage in)
Unfezant vs Ninjask: Ninjask (this should be a really exciting aerial battle, but though Unfezant has the type advantage, it looses in a quite close fight due to Ninjask's superior speed + maybe due to taking prior damage)
*To continue avoiding Toxic Spikes, Alain now sends out Metagross*
Metagross vs Ninjask: Ninjask (being a far more stronger Pokemon, Metagross easily gets the revenge kill by shrugging off Ninjask's ineffective moves)
Metagross vs Ursaring: Ursaring recalled (after Paul sees Urasring getting easily overwhelmed and smacked around by Metagross' superior attack power and speed, he recalls it in time to avoid a loss)
*Seeing that Metagross is a real heavyweight, Paul sends out his starter and one of his strongest Pokemon Torterra to counter it*
Metagross vs Torterra: Metagross (would be quite a close fight, but as Metagross has barely taken damage fr the previous two fights, plus is the slightly better Pokemon, amd resists all of Torterra's moves, it pulls off the win)
*Seeing that Metagross has taken a lot of damage and is really exhausted, Alain recalls it and sets out Bisharp, who won't be affected by Toxic Spiles as well, and Paul sends out Ursaring to counter it*
Bisharp vs Ursaring: Bisharp (after a close fight, Ursaring has the moveset advantage with 4x effective Focus Blast and Hammer Arm, but Bisharp has superior speed to counter it + the deadly Guillotine. If Ursaring activates Guts being paralysed by Bisharp's Thunder Wave then the fight is even more close, but since Ursaring has taken significant damage from Metagross beforehand, Bisharp obviously wins)
Bisharp vs Drapion: Drapion (Due to Bisharp being quite worn out from the previous fight, Drapion wins comfortably, but due to Bisharp's immunity to Poison type moves, it still is able to get some damage in)
*Alain decides to continue avoiding Toxic Spikes and sends out Charizard in the air for that purpose*
Charizard vs Drapion: Charizard (Charizard wins without barely taking any damage due to being the far stronger Pokemon and Drapion taking some damage from Bisharp beforhand)
Charizard vs Electivire: Charizard (being Paul's strongest Pokemon and having a type advantage, Electivure puts up a valiantly close fight but still falls to Charizard's superior strength eventually, giving a definitive win to Charizard)
Thus, Alain in this case, wins 6-3 with having a significantly damaged and weared down Charizard, a heavily damaged Metagross and an unused Weavile left in his arsenal.