That seems to be completely different story from the previous posts. However, you could try to change UnresolveUrl(string url)
and remove the condition where we are checking for the length and whether the url starts with slash. Then you can check whether the url.Equals("/") and concatenate the subdomain, return the domain root and the url.
Also the example is prepared for old version of Sitefinity, if you have made any changes to it and cannot sort out the issue, let us know.
the Telerik team