Enabling Cross-premises delegate access

No satisfactory resolution for my support request.  I have moved on to trying to work around this problem for migrating delegates and Managers.  We are going to have to try and move them all together in batches of interconnected accounts.

Unfortunately this is all I received for an explanation when they archived my case, I haven't added anything on the feedback page yet: 

Issue:

assign on-prem delegates from o365 mailbox.

Resolution:

Outlook delegate permission wont work in cross-premises in Office 365.

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