I'm going to say this is not possible due because `vim` is not executing remote commands. It is simply using `scp` to copy the file over, edit it locally and `scp` it back when done. As stated in [this question](http://askubuntu.com/questions/208378/how-do-i-copy-files-that-need-root-access-with-scp) `sudo` via `scp` is not possible and it is recommended that you either modify permissions to accomplish what you're wanting or just ssh across to the remote machine.