As mentioned in the article, Vagrant actually comes with built-in support [1] to run Docker containers. Ideally it would obviate the need to do some of the manual work done here to get this type of environment up and running.
The Vagrant support for Docker uses boot2docker, which only supports VirtualBox, so I’m left high and dry.
You can use a proxy Vagrantfile to configure the type of machine that is used as the Docker host [2]. Unfortunately there is a bug [3] that make this not quite usable yet.