RG Live WotLK 3.3.5a

If Frost Warding procs and damage is negated, it should still proc Incanter's Absorption (counts as absorb).

Sources:

https://criticalqq.wordpress.com/2009/05/14/incanters-absorption/

Any damage negated from Frost Warding counts towards Incanter’s Absorption.

https://www.wowhead.com/forums&topic=162825

If the the 30% to negate damage procs, does Incanter's Absorption count this as an absorption?
The answer to your question is yes.

https://www.mmo-champion.com/threads/696642-Incanter-s-Absorption

You can still get a quite a lot heckloads of spell power if you're lucky on a frost warding proc (blood princes fireball thingy, 14kish frostbolts from lady deathwhisper hc etc.)

https://www.mmo-champion.com/threads/696642-Incanter-s-Absorption?p=7345150&viewfull=1#post7345150

It's an absorb and it procs the IA.

http://www.arenajunkies.com/topic/128271-incanters-absorption-changes/

The important bit, frost warding activates this!