Slightly different problem. IRT is geared toward one or a very limited operator set, so best to directly connect Skype to Skype without the IRT software getting involved. So don't think there is a big problem there.
The same software is being used as in the Webxcvr and IRBHost. The VB6 is used with a VB module provided a while ago by Skype. The VB6 software can read the Skype interface and is able to initiate a call and terminate a call, i.e. with the older versions of Skype.
There have been a lot of upgrades by Microsoft over the years, e.g. VB.Net, etc which are not reflected in the old remoting software. I think the best thing to do would be to totally rewrite it using a more modern and hence supported language, such as C++, etc. That is a much larger job than I want to tackle at this time. After spending over 10 years in this area, I have moved on and out of software related activities.
I believe that the technology for remoting now is something like interactive Flash, etc that will be consistent over computers and mobile devices. Again not in my job jar these days.
Stan