If the workbook is created locally on a pc that has internet access, then it will be able to access google analytics. The users can then publish that workbook to Tableau Server since all GA workbooks utilize extracts, and it should continue to work. However, the server can not be setup to refresh that workbook since the server has no access.
Options - the user could update the viz each X periods based on the needs of the viewer. This could even be with done automatically each day using the -refreshextract option from the command line with a local copy of tableau desktop.
the command would be something like
tableau refreshextract --datasoruce "GoogleAnalytics" -c configfile.txt
Online help covers this topic here: Tableau Data Extract Command-Line Utility
I hope this helps.