No. But the users should be made aware that their content will now be accessible by the organization if they opt to associate the ID to the business. Per the migration steps, Apple gives this guidance: Find My, Health and services restricted by your organization will not be accessible.
If a user is using a device that contains Find My, Health, or the services available in ABM/ASM for individual activation (iCloud, collaboration, Messages, FaceTime, Developer, AppleSeed). These are controlled under Access Management > Apple Services.
Hope this helps. Make friends with your mail administrator and ask for a mail log report so you know which users are notified.