The only way to shoot through the driver side window and not see the camera is to be far enough off-angle to not be reflected in the glass.
If the camera is flat-on enough to be reflected in the glass, then putting black around the camera won't help because then you'll just see a black shape reflected in the glass, and if you enlarge the black shape so that it fills the glass, then you won't have any reflections at all in the glass. And if the camera is at an angle that it can see itself reflected, then a polarizing filter is not going to remove that reflection, the polarizer works best dealing with reflections at the opposite angle to the camera's position.
Where a polarizer is useful is when you get the camera at enough of an angle to not be reflected, then you can use the polarizer to control the heaviness of the reflections over the actor's face.
Today, many productions would roll down the window so that they can shoot the driver in profile from outside their door, and if they want to, they can add reflections in post as if the window was rolled up, if they shoot a clean plate of what would be going by in the glass reflection.
