Lights through Transparent pixels

I have a video file with a transparency of two characters. It is on a 3D image plane and set into a merge 3D with a camera projected room using 3d image planes.
Is there a way to get the light to shine through the transparent parts of the video file to create a cast shadow of the characters? As of right now it only cast shadows in the shape of the plane as a whole.
PS - the cast shadow of the window in the floor is painted in the texture so that's not real.

Is there a way to get the light to shine through the transparent parts of the video file to create a cast shadow of the characters? As of right now it only cast shadows in the shape of the plane as a whole.
PS - the cast shadow of the window in the floor is painted in the texture so that's not real.
