If you haven't found out by now, the Repair All feature which is supposed to show up on the world map, only shows up when one or more houses are in need of a repair. Usually these houses are around 80 or 70% durability or lower.

It works the same as it does with the 360 it seems. You and the person you choose to play with must both own the same downloadable content. If one person has something that you don't and vice versa, you can't play together. The only way to bypass this however seems to be the quick match option but that is still speculation.

Just in case you didn't see the pop-up when you started up Steam, derp.

http://i34.photobucket.com/albums/d137/Shadow_Flame/General%20stuff/fable-3-1.jpg