Steps to reproduce:
1. Add the following script to any project:
Texture2D screenshot;
void OnGUI()
{
if (screenshot != null) {
GUI.DrawTexture (new Rect (0, 30, 128,128), screenshot);
}
if (GUILayout.Button ("Take", GUILayout.MinHeight(64)))
{
int width = Screen.width;
int height = Screen.height;
screenshot = new Texture2D(width, height, TextureFormat.RGB24, false);
screenshot.ReadPixels(new Rect(0, 0, width, height), 0, 0);
screenshot.Apply();
}

}
2. Deploy to Windows Phone 8
3. Orientate device to landscape orientation
4. Click on "Take" button. Image will appear rotated.