This is an old thread, but I could not find anything about a script to import classlist files into an existing course.
So, I hacked up and am testing a new script for importing a classlist file into an existing course. At present, it borrows code from lib/WeBWorK/ContentGenerator/Instructor/UserList2.pm but in the long run, the core code should be moved to a new module file in lib/WeBWorK/Utils and the called from the script and the UserList2.pm files.
Note: It is currently set up to add users which do not exist, but to skip (and not replace) users which already exist in the course.
I have done some initial testing when the script is put in webwork2/bin and run using syntax like:
./importClassList.pl courseName path_to/classlist.lst
Any feedback would be welcome.