I had a company-owned MacBook Pro that was locked to an Apple ID using a company email address. Whilst I had the Apple ID password, I only discovered that the laptop was locked to a personal Apple ID after we had enabled federation in ABM, and so all Apple IDs using [email protected] were claimed by ABM.

This then presented a problem as I couldn’t log in to turn off Activation Lock on the MacBook Pro as I didn’t know what the temporary Apple ID was.

Fortunately I found hidden in an Apple help article some information that pointed me in the right direction to guess it.

https://support.apple.com/en-us/102159

The format for a temporary Apple ID follows a pretty clear pattern:

[email protected] would then become
[email protected]

I was able to log in with this temporary Apple ID and the password that I already had, and then change it to an @iCloud.com email address to unlock the Mac.