A SMB of 90 users is considering moving to Office 365 E1 plan, with a setup of Cloud Identity + Dirsync. One department of 15 users relies heavily on calendar sharing. As soon as email is migrated, this department will likely exchange invitations for calendar sharing with full control, add the 14 other users calendars to their outlook client, and be editing multiple calendars throughout the day.
Is this a reasonable expectation? If there is a possibility that this will cause issues, I would want to plan in advance for alternate solutions to their needs.