Examples from Fitday:
1 cup celery juice: 10 g carb
8 ounces Kale (6 oz juice?): 22 g carb
1 cup carrot juice: 22 g carbs
2 small avocados: 15 carbs
2 cups diced cucumber (8 oz juice?): 6 carbs <-- hey, not bad.
While I wouldn't call those sugar "bombs," those carbs do add up, especially if you've taken out all the fiber. If you're going to alternate low-carb juice with bone broth, that may not be a bad thing, but I don't see how you could tolerate 40 days of it.
5'0" female, 45 years old. Started Primal October 31, 2011, at a skinny fat 111.5 lbs. Low weight: 99.5 lb on a fast. Gained back to 115(!) on SAD chocolate, potato chips, and stress. Currently 111.