This may make things even more difficult, but let's see what happens.
Let's say I created a user called generic@mydomain.com and gave said account a Microsoft Exchange Online P1 license.
Then I created some shared mailboxes:
rmm@mydoamin.com
support@mydomain.com. Then added aliases of billing and sales to this shared mailbox. Then I give generic@mydomain.com delegated access (full) to these mailboxes.
On the OAUTH part of ITFlow, if I logged in as generic@mydomain.com, would it be able to see those shared mailboxes and be able to pull email from them?