Great question. As you've already alluded, renal transplant patients with HCV have a lower mortality than renal transplant patients that are HCV-free. In one small study, at 8-years, almost 17.5% of renal transplant patients developed cirrhosis as a result of HCV. And as you correctly indicated, the larger mortality rates is directly related to HCV-induced liver disease.
Now, just for review: in the pre-transplant HCV+ patient, the best therapy would be IFN-alpha + ribavarin. Unfortunately, most CKD (and all ESRD) patients are not given ribavarin because of its renal clearance (toxic levels of ribavarin can cause serious hemolytic anemia). INF-alpha monotherapy is not as effective as dual therapy, and there are many failures with monotherapy. Thus, CKD and ESRD patients are already at a disadvantage because the only therapy that they can receive to kill HCV is not very effective.
Post-transplant patients should be able to take both IFN-alpha + ribavarin, except that IFN-alpha has been known to accelerate/promote acute rejections. Thus, there are many centers that would not treat HCV in the renal transplant patient for fear of rejections. The one exception would be HCV-induced MPGN (via cryoglobulinemia) of the renal transplant; in this case, IFN-alpha +/- ribavarin would be used to save the allograft.
You've probably read about Pegylated interferon. I'll keep this portion short, because it is not widely used to treat post-transplant HCV+ patients. More data is required in this select patient population, but I'd keep my eye out for it in the future.
Finally, one of the best ways of treating HCV in the post-transplant patient is to perform a dual liver-kidney transplant. There are some strict indications for the dual transplant procedure, which you can learn about here.