OP penalties and HQ bonus

[gingerbread]

In MG, Guards Armoured HQ says -100% penalties. I did assume that this means that units will not pay any (enemy) unit induced OP penalty, but will still pay residue/congestion etc. However, whan moving into a hex (the one adjacent to the 2 front germans) with 15 OP penalty, my GA unit still pays full cost! I assume that some of the 15 OP penalty derives from E-ZOC and would therefore be reduced.

I'd like a breakdown on what type of OP penalties are reduced by the HQ bonus.

/g