Answer
No — fields from a Custom Logical Unit can't be pulled directly into a Report Designer report; the report's XML generation logic doesn't include custom-LU fields the way it includes fields from the standard LU(s) the report is actually built against. The workaround is to reference the custom LU's data indirectly: add custom fields to the existing standard Logical Unit that the target operational report is already built on (using a Select-statement custom field referencing your Custom LU's data), and then use those standard-LU custom fields in the report layout instead of trying to pull from the Custom LU directly.