Not sure what's wrong in your case. For me both parameters (.Path, .FriendlyPath) work flawlessly. Anyway, glad to hear you've found the way to achieve your goal.
Just stumbled over this issue. The TargetDir-Property is not a string (Get-VBRJob -Name $jobname | select TargetDir might suggest); it's an object of Type CLegacyPath that has only one Property IsVbm. What you're probably interested in is it's ToString() Method.
So, what you probably want is (Get-VBRJob -Name $jobname).TargetDir.ToString()