Essentially blackpoint is intended to consists of a sub-set of blackpearl for customers who have less complex workflow needs. When they progress to the point where they have more complex requirements, they will be able to upgrade to blackpearl. This upgrade factor will probably come in after blackpoint RTM and blackpearl SP2 is released.
The base server components are similar so essentially you can't run them together. i.e. there is a service component, similar databases, etc.