Yes, this can be specified in the user list TSV file.
A new column will need to be created in the TSV file called "PstDir". Under this column specify the location of the PST file to be created in, for example:
\\dirname\username\ <file://dirname/username/>
c:\dirname\username <file:///c:/dirname/username>
For futher details, please refer to solution 13528 titled: "What columns can I add or modify in the 'UsersToMigrate.tsv' file?": http://questsupportlink.quest.com/eSupport/Solution.asp?WAid=268456392&itemID=13528
