Sharing Process Servers Between Version

The CPS version at my company is 6.0.2. We are going to a later version of CPS (7 or 8, not sure yet) and want to know if the process servers can be shared between the 6 version and the 7 or 8 version. We are wanting to migrate jobs gradually instead of the big bang approach. We have a fair amount of complex jobs that will take considerable time to upgrade and test in the new version. The goal is to keep the current number of process servers to minimize the cost of moving to the newer version. Any information would be appreciated.