No, the Pokemon you get in the In Game Trades are just as Random in the stats and Shiny as catching a wild one. If you want to Offer a Shiny, Which i'd suggest not, You will most likely not get one in return. The best thing to do in those Trades, is to offer one that has bad stas, etc. Save in front of them, and keep Trading until you get one Shiny. I saved in front of Bebe who gives you an Eevee, Granted it's not a Trade, But it's basically the same in Randomness. Each time i get Eevee, it has different stats each time. So i'll keep doing it until i get one i want.