Pokemon bred from transferred Pokemon were obtained in Kalos, and thus would have the regional mark to make them legal. However, the upcoming tournament explicitly states that only Pokemon in the regional dex are allowed, so even if you did breed them to obtain legal versions of those transferred Pokemon, they'd still be disqualified unless they already appear in the regional dex.
In future tournaments, that rule will most likely no longer apply, and the entire Pokedex will be legal. But, I wouldn't be surprised if they still kept the Kalos Mark rule from here on out, to completely lock out any hacks or Move Tutors from Gen V and prior. But using their offspring hatched in Kalos should not be a problem.
Pokemon Y FC: 1177-7400-8683 Safari: Kakuna, Whirlipede, Venomoth