Activity/BPM/Workflow Migration

We are looking at migrating existing data from a legacy system to a new system based on the CUBA platform. We are using the BPM Activitii addon to define processes in the new system, the problem is that the migrated data will need to be migrated mid-process to various points in the Activitii workflow. Anyone have any experience or guidance on how I can go about doing this? I’ve seen a forum that suggested using Message Start events in Activitii. Does Cuba support this? Thanks.