It's a moot point, since I quoted the rule in the edit to my post (it's under rods in the magic item section), but show me an implement class feature for wizards that lets you use all three of wands, staffs, and orb implements. The class feature, from what I can tell, is called Arcane Implement Mastery, and gives you a power with one type of implement. There is no class feature that says "you can use staffs, orbs, and wands" as far as I can tell. It's implied in the "Implements" color text which is not in the class features section, but I do not see an actual class feature with that kind of text.
You also don't see class features that give them 4 hit points every time they gain a level, proficiency in cloth, daggers, and the quarterstaff, +2 to their Will, or say they get the Arcane skill and three others from a fairly explicit list.
However, you'll note, those are -very much- rules that determine the class traits.
Of course, reading the section entitled 'Implements' says, explicitly:
"A wizard wielding a magic orb, staff, or wand can add its enhancement bonus to the attack rolls and damage rolls of wizard powers, as well as wizard paragon path powers, that have the Implement keyword."
There's your rule.
It's reiterated under 'Arcane Implement' under Adventuring Gear on page 221.
"Wizards use Orbs, staffs, or wands as focus items for their spells, while warlocks use rods or wands. Using a nonmagical implement confers no benefit. You can purchase a magic implement to gain an enhancement bonus to attack rolls and damage rolls with your arcane powers."
So, here's the way to look at it, specific breaking generic fashion.
Generic: Implements do nothing for you.
Specific: If your class explicitly permits it, you can use an implement's enhancement bonus for your attack and damage rolls on powers of -that- class, and only if they have the Implement keyword.
Lastly, so you never need to worry about it, this is the complete list of implements, and the classes that use them. In order to use an implement, the power must have the Implement Keyword, and you must be of that power's class, or receive permission from that class's multiclass feat.
Holy Symbols (including weapons that have the property of being a holy symbol): Cleric, Paladin
Wands: Artificer, Warlock, Wizard
Staves: Wizard, Artificer
Rods: Warlock, Artificer
Orbs: Wizard, Artificer
Pact weapons: Warlock
Light Blades: Swordmage
Heavy Blades: Swordmage
There is no current Implement in the rules for Spellscarred implement powers, as far as I am aware.