Will I Lose Fat from Brazilian Butt Lift if I Do Butt Workouts?

The fat lost during a workout after 6 weeks will be proportional to that of the surounding areas, In fact it will actually help improve the appearence of the brazilian butt lift and its recomended that to maximize results that you work out, low intensity at first, to help tone that fat and muscle.

After a Brazilian Butt Lift (BBL), doing butt workouts will not cause you to lose the fat that was injected into your buttocks directly. The fat cells transferred to your buttocks behave like the fat in other areas of your body. If you lose weight overall through diet or exercise, the fat cells in your buttocks will shrink alongside fat cells in other parts of your body, potentially reducing the volume of your BBL.
However, if you focus on targeted gluteal exercises (like squats or lunges), you may build muscle in your glutes, which can help shape and define your buttocks, improving the appearance of your BBL. These exercises can enhance the contour and firmness of your butt without specifically burning the transferred fat.
It’s important to note that you should follow your surgeon's post-operative instructions, especially in the early stages of recovery. Consult with your surgeon about when it's safe to resume exercise and how to gradually progress in intensity to maintain the best possible results from your BBL.
Krishna Vyas, MD, PhD, MHSHarvard, Hopkins, & Mayo Clinic Trained Aesthetic Plastic SurgeonNew York, New York

Depends on the workout you do. If you're doing cardio to burn fat then the fat in your buttocks will most certainly decrease. If you're doing weight lifting then the muscle you grow in your buttocks will add to the fat volume that's already there!