when I went to the H and A site, on the block heater for the 06 Civics, it states 'not for hybrid' making me assume that they did something different with them. It sounds like you had a good workout trying to get that off. Reminds me of when I was trying to change a O2 sesnor on an 89 Isuzu I-Mark. I couldn't get it off (I was using an O2 socket) and I ended up bending the wrench and adapter (but not the 02 socket). I didn't even use a breaker bar, I did try using several sprays to try and loosen up any rust/etc. that may have been locking it up.

Anyway, I would double check on if the block heater can even be applied to the car. I don't see why they would exclude it completely for the Hybrids, but it almost sounds like you were trying to remove a piece that wasn't seperate (not an actual bolt, but just a casted bolt head shape >_< ) Good luck, hope they get it on there for you and treat your car kindly!