In GT++ 1.6.99, the mods correctly strips Mekanism items of their Forge Ore Dictionary entries, which means that the Mekanism Ore and Circuits are useless for GregTech progression.

In GT++ 1.6.103 and GT++ 1.6.110, this modification is no longer in effect, and Mekanism circuits and ore can freely be used by GregTech.

Issue currently ongoing, reverting back to GT++ 1.6.99 restores this change.

GregTech 05.09.32pre1
IC2 2.2.827-experimental
GT++ Single Player
Issue Class: Minor

Couldn't reproduce this issue.
User said issue has been resolve since 1.7.0-preX.

Closing for the time being.