I agree that anything is possible in Photoshop. And it isn't the best photo to start with, so easier to hide an edit. But I agree with 2ndGen. Not that it is the best Photoshop I've seen, but that it doesn't scream "edit" to me. As 2ndGen says the back glass is different, the roof is different, wheelwells, etc. Add in that the back door handle is different from the front one, you can see the rear seat through the window and the rear roof pillar, and the reflections in the glass "work." If it is a Photoshop, he went to a fair amount of trouble for a crummy picture.
Actually, that is another thing. I find it harder to "shop" a low resolution photo than a high resolution one. The more pixels you have, the easier it is to blend things. Now, it is possible that he started with a better photo and then cut down the resolution at the end to hide his sins...
Still, even if a "shop" it is a pretty cool idea.