When I break a renamed minecart (doesn't matter what type of) in creative mod, it gives me the item of it.

With the minecart chest, it gives me a renamed minecart and a chest, with the minecart hopper it gives me a renamed minecart and a hopper, etc.

I also note that the minecart command block only gives me the minecart item, it doesn't give me the command block. (But i'm not shure if that is a bug or not...)