The body stores calories--how it gets stored depends somewhat on the type of calories. Lean protein is a form that doesn't very readily get stored as fat. But as long as you eat less calories than you're burning, you're going to lose fat. Period.
In any case, if you're doing toning exercises and cardio and doing a strict diet, it's very important to get enough lean protein to maintain muscle mass--as you don't want to lose that as you'll look like shit and slow down your metabolism.
Low calorie whey protein is a good source of lean protein.
Ok, I've really got to say this:
any of the three macronutrients will be stored as fat IF they are not being utilized. There's no such thing as LEAN protein dietary protein is dietary protein. Now, there are different grades in the bio-availability department (ie. Egg white albumen is more easily digested than meat, and why is more easily digested than egg whites), but protein is protein and it's used by the body to maintain a positive nitrogen balance which, if you have and under the condition of proper resistance training, will facilitate muscle growth.
Now, if you're saying "lean" as in you're not eating a bigmac or something, then yes, I agree, but that's more of a "dirty" FOOD in general.
As for the assertion that you'll burn fat in a caloric deficit, this is true, HOWEVER, after a certain point your body starts going for the tissue that uses the most energy: Muscle. This is why dieting almost always causes a loss in strength. When a bodybuilder "cuts", he expects to lose a certain amount of lean mass and strength. If your bodyfat is low (sub 12), the loss in lean mass becomes even more pronounced. This is why if you're fat and weak, after some time dieting and training you'll have some new muscle and be thinner. This doesn't last forever.
If you're dieting down, the best bet is to eat 100-200 calories less than you normally do a day, and adjust if you're losing more than 2lbs a week (after you lose water weight and excess glycogen stores). This is the best way to make sure you don't cut off a ton of lean mass. It's slower, but it'll be better in the end. Scale back on simple carbohydrates and fats, and you'll see a huge difference.