Q:

Does Spell Vamp affect magic damage procs from items?

I've been pondering how best to build Ezreal in the new Dominion mode, and it's gotten me wondering: Are Magic Damage procs, like from Wit's End and Madred's / Kitae's Bloodrazor affected by the aggressing champion's spellvamp? 
I know they don't get counted as part of the base damage of the attack, i.e., a separate damage number appears, and proc-boosted attacks don't generate more lifesteal than expected, but are they considered for spell vamp at all? 
I know, for a time, the Wriggle's Lantern, 500 damage vs. minions proc, triggered lifesteal (which, given that it was 500 bonus damage, was quite noticable) but that has been patched out. 

A:

The Spell Vamp portion of the LoL Wiki and my own experience show that  

[Spell Vamp] works off of activated item effects, summoner spells, and abilities, regardless of the type of damage done.

Therefore, items that give proc effects to attacks like Bloodrazor, Wit's End, Malady, Wriggles etc, will NOT grant the user health through spell vamp.
On a side note, Ezreal's Mystic Shot (Q) applies on hit effects, including but not limited to, lifesteal.

