I have replaced internally routed cables/housing once on my Orbea Avant. I bought the Shimano routing tool, but, after doing the work, I realized I could have done it without the tool with no more time and hassle involved. I dreaded doing it the first time, but I am pretty sure if/when I do it again, it will go a lot quicker. I believe different manufactures use different techniques in the routing, ergo, there will be some differences in the replacement process. It seems likely to me that frame sets with oversized tubing make it a bit easier.