WORKAROUND: The results exported to CSV or Excel do include the leading zeros and this can be verified via a straight text editor (such as Notepad). When opening the file in Excel; Excel will strip these leading zeros.
If the results are needed in Excel, it is possible to import the CSV into Excel and have Excel keep the leading zeros via this method:
'Column Data Format' section.
The leading zeros will still be there in the new worksheet with the imported data.
STATUS: This has been corrected in TPAM 2.5.917.
From the 2.5.917 Release Notes under "Resolved Issues":
"The List User ID’s report, when exported to Excel, does not retain leading zeros in User ID name. BFER 8544"