Are the new gang hideouts added in "The Liars and Cheats" DLC multiplayer-only?

The Liars and Cheats DLC (Rockstar page) adds seven gang hideouts to the game. When visiting Crooked Toes — an area with a distinct rock formation — both at night and during daytime there was no activity in the region. Do the hideouts only appear in the online multiplayer?

I have the Game of the Year edition (includes all DLC) on Xbox 360.

Solution 1:

The Hideouts added by The Liars and Cheats DLC are only available in Free Roam (multiplayer).

As the wiki states:

The Liars and Cheats DLC adds seven hideouts to Free Roam that are not available with the base game. Upon completion of any of the gang hideouts added by this DLC, an Explosive Rifle is awarded to the top player.