Illustrator file is not just simple one image, that there will be a single image height, width and bit depth available. Illustrator file is made of two components, one is PDF and another is Illustrator private data called PGF. PDF spec is available to everyone while PGF has very limited documentation, but both of them are vector based format, it can contain paths, images, gradient, text etc. They can have multiple pages of varied sizes and each page can have multiple images. So there is no single image height, width or bit depth for the entire file in total.
