Eu finalmente fiz isso usando o PowerShell. Agradecemos aos seguintes posts do TechNet Referência do GUID do Exchange 2007 e Atualizar o esqueleto da ACL Eu consegui delegar o controle da unidade organizacional TestUsers a um usuário NickA e dar as permissões que eu postei originalmente.
$OU = Get-ADOrganizationalUnit -Identity "OU=TestUsers,DC=contoso,DC=private"
$SID = new-object System.Security.Principal.SecurityIdentifier $(Get-ADUser "NickA").SID
$GUIDUserOBJ = new-object Guid bf967aba-0de6-11d0-a285-00aa003049e2
$GUIDGroupOBJ = new-object Guid bf967a9c-0de6-11d0-a285-00aa003049e2
$GUIDNull = new-object Guid 00000000-0000-0000-0000-000000000000
$ACL = Get-ACL -Path "AD:$($OU.DistinguishedName)"
#Create a hashtable to store the GUID value of each schema class and attribute
$ADRootDSE = Get-ADRootDSE
$GUIDMap = @{}
Get-ADObject -SearchBase ($ADRootDSE.SchemaNamingContext) -LDAPFilter "(schemaidguid=*)" -Properties lDAPDisplayName,schemaIDGUID | % {$GUIDMap[$_.lDAPDisplayName]=[System.GUID]$_.schemaIDGUID}
$ACL.AddAccessRule((New-Object System.DirectoryServices.ActiveDirectoryAccessRule $SID,"CreateChild,DeleteChild","Allow",$GUIDUserOBJ,"ALL"))
$ACL.AddAccessRule((New-Object System.DirectoryServices.ActiveDirectoryAccessRule $SID,"GenericAll","Allow",$GUIDNull,"Descendents",$GUIDMap["user"]))
$ACL.AddAccessRule((New-Object System.DirectoryServices.ActiveDirectoryAccessRule $SID,"CreateChild,DeleteChild","Allow",$GUIDGroupOBJ,"ALL"))
$ACL.AddAccessRule((New-Object System.DirectoryServices.ActiveDirectoryAccessRule $SID,"GenericAll","Allow",$GUIDNull,"Descendents",$GUIDMap["group"]))
Set-ACL -ACLObject $ACL -Path "AD:$($OU.DistinguishedName)"