It seems you can boost core race characters and get your heritage armor, but you have to be exalted with your faction.
See:
- Blizzard Support - Earning a Core Race Heritage Armor (battle.net)
- Can Boosted Characters Get Heritage Armor? - Community / General Discussion - World of Warcraft Forums (blizzard.com)
- Can I still boost core classes and get heritage armor? - Community / General Discussion - World of Warcraft Forums (blizzard.com)
- Heritage armor and character boosting - Community / General Discussion - World of Warcraft Forums (blizzard.com)