Containers spun up depend on the provider, so if you deploy to Amazon it's going to spin up an AWS instance. However, if you're deploying to an Open Stack provider it all depends on the Open Stack configuration. Juju doesn't quite care what the provider does with regards to virtualization software.

However, for development you can setup a "local" provider (http://askubuntu.com/questions/65359/how-do-i-configure-juju...) and deploy to your own machine using LXC. This makes development quick and affordable and makes it easy to test drive Juju without needing to use a cloud provider.