We're in the process of an AD migration project. I want to find out whether it's possible to unjoin the BES from domain A and join it to domain B. Both domains are in the *same* forest.
The users on the BES can't change Exchange Organizations without an EA activation. So, if you're looking at doing this without affecting the users, no it can't since the EO is based off of AD, which is based off of domains.
Yup, the besadmin account has full access in both domains. Although we have two child domains in the forest, we only have one Exchange organization. (You can't have multiple exchange org in a forest anyway!)