Abilities that trigger on the return (such as the gaining of an ability, or the draw on Provisions) happen when the card returns. The ability that is gained activates when the character enters battle.
I think gained abilities only activate when the character enters battle. In this specific example, at best, the TC applies to the ability and it activates every time the character enters territory, allowing a heal then, but the gained ability is not worded such that it could be used at any time.