Dear,
Mainly for PM the cut over activities are Preventive/Calibration/Performance based Maintenance needs to be carried out as per the legacy system dates from go-live date.
So first of all,you need to identify the all the technical object of maintenance strategies.Based on these strategies create strategies and task list lists for Preventive/Calibration/Performance based ,Maintenance.
Mainly for performance maintenance activities, measurement documents should be in place with counter readings to trigger maintenance orders .
For ongoing maintenance activities, you can create maintenance order on go-live date and assign the materials,and can trigger P.R for services.Any way the MM side , stock will be updated as on date.
To have PM schedule as per the legacy system, you need to be care full while assigning the start date of the PM plans.Here i suggest you can put the latest Preventive/Calibration done date and for /Performance Maint., you need to create a measurement document for the latest reading.
Regards,
pardhu