01 Jun 2007 at 03:52 - 5
If any character uses a skill trainer to purchase... Oh, let's say Healing Breeze... Then that skill is "unlocked".
Any PvP players may use it,
Your heroes can use it,
Any PvE players MAY NOT use it (they have to buy it themselves. These skills will be marked "unlocked" in the Skill Trainer's list, as opposed to "Known")
I guess I am telling you all this to explain how it applies to any situation, but the answer to your specific one is: YES. Using Balthazar faction to unlock a skill makes that skill "unlocked" by definition of the Tome. (Obviously, you will need an Elite Tome for Elite Skills.)
HINT: Capping skills also unlocks them, so you can teach one of your characters a (elite) skill capped by another.