It is possible, any reputable bodyshop will use a special bodywash solvent which is specifically designed to remove the silicon, waxes etc. Even more crucially they should use a special etching primer for the plastic.
Be warned though there are some very dodgey bodyshops. As I discovered with my local VW/Audi/BMW APPROVED bodyshop. It took them 4 attempts to paint my S4 bumpers the correct colour then with no defects then to repair the damage they caused to the wing and roof of my car then by compensation I foolishly asked them to re-spray the stone chips on the bonnet that took 2 attempts until they got the pin holes out of the lacquer generally caused by not removing silicone / waxes correctly and all this took 4 weeks!
So make sure you have it in writing before you have the car taken in that
A. You walk round the car with the foreman and sign off on all existing damage, jsut as you would with a hired car.
B. If you are not happy with their workmanship then they will make good.
C. It should come with at least a 3 year warranty
C. If you don't know good paintwork from bad take someone that does.
I was amazed to find my friends recent purchase had been independently inspected and approved by a major auto association with no prior body work. I noticed immediately that the rear bumper had been resprayed. He's now seeking compensation!