i've always been bugged by the fact the 3rd dlc was never fixed in the pc version of guerrilla, i.e. it never worked.
i managed to unlock the 6 new maps for wrecking crew that are in the smasher pack (dlc3) you still need the patch from faction files if you wish to play the walker mode as well.
replace the interface & misc vpp files in the pc/cache folder.
the new maps will appear in the wc menu;
There was meant to be 8 maps like on the 360 & PS3 but some of the files weren't included in the pc version. (STRATOSPHERE & INVASION)