As far as I can make out so far it is not designed to be multitenant. Each client gets an instance for their apps which can consist of multiple VMs. Based on interpreting the install guide here https://github.com/cloudfoundry/vcap
Currently the multi-tenancy is based on locked down unix users and permissions and other system hardening, pretty much same approach Heroku uses so you judge whether that's multi-tenant or not. We are looking into lightweight containers like lxc and friends for another implementation of the multi-tenancy.