I would try opening the CSV in Excel, formatting the field as Text, saving in Excel, and importing the Excel file into Tableau.
Agreed. Or get the outputing mechanisim to put quotes around the numbers.
When importing in Excel 2010 use Data >> From Text :
Step 2 of 3: Set your delimiter to Other and type in the pipe symbol. Click Next >
Step 3 of 3: Select each of the first three columns and set each one to Text. This insures the leading zeros will appear. Click Finish.
Do you need the leading zeros? You could LEFT or RIGHT them out.