Take a look at the ingredients...
here is what is the slim fast ones...
Water, Calcium Caseinate, Milk Protein Concentrate, Canola Oil, Cocoa (Processed With Alkali), Potassium Phosphate, Mono and Diglycerides, Cellulose Gel, Glycerine, Maltodextrin, Cellulose Gum, Salt, Soybean Lecithin, Guar Gum, Sucralose (A Nonnutritive Sweetener), Artificial Flavor, Carrageenan, Sodium Citrate and Citric Acid. Vitamins and Minerals: Magnesium Phosphate, Sodium Ascorbate, Calcium Phosphate, Vitamin E Acetate, Zinc Gluconate, Ferric Orthophosphate, Niacinamide, Calcium Pantothenate, Manganese Sulfate, Vitamin A Palmitate, Pyridoxine Hydrochloride, Riboflavin, Thiamin Mononitrate, Folic Acid, Chromium Chloride, Biotin, Sodium Molybdate, Potassium Iodide, Phylloquinone (Vitamin K1), Sodium Selenite, Cyanocobalamin (Vitamin B12) and Cholecalciferol (Vitamin D3).
a big part of the SBD plan is eating "whole" foods... I, myself, wouldn't want to drink canola oil and its one of the first ingredients! I prefer to spend my 200 calories eating a nice big salad with some beans and dressing...
Most of the ingredients I see aren't in my vocabulary and I try to stay away from that stuff

As for if its ok on p1 or even 2 of the plan, well, I wouldn't use them but maybe others have more insight on this-I just don't know that these ingredients are allowed.