HostedMigration 510 error : the user could not be moved because the tenant has not been enabled for shared SIP address spaces
AS a pre-requisite, you would have configured your tenant to allow a shared Sip address space using
Set-CsTenantFederationConfiguration -SharedSipAddressSpace $true
However, even after waiting (for a while), moving a user using the Move-CsUser command still fails with the same error.
While technically using the same mechanism, you may may want to try using the "Move selected users to Skype for Business Online…" option in the Control Panel of Skype for Business 2015, after which the following attempts using Move-CsUser will start working.