The Swiss have a through train that runs on two track networks with different gauges and platform heights. They do this with bogies that change gauge and height while the train is moving.
I know what the video showed me physically. But what is its purpose? What operational circumstances would require such action? Maybe a bogey manufacturer wants to serve a market of different gauges around the world. But why would the bogey need to change gauges on the fly?
Wow. Someone had a very creative mind! I can see where this saves all kinds of time, and money in the process. How widespread is this use at present?
When our family lived in Europe in the 80s we'd always do trips in the summer. My dad, also being a train buff, made sure we hit the most interesting trains so we did the TGV which was only a few years old at the time, some neat trains in Austria and Switzerland, and the Talgo in Spain. He told me the special thing about the Talgo was that it changed gauge along the trip. I remember the train pulling in, and I think they did one car at a time, or one bogie at a time and the process took awhile from what I remember. Maybe 15 to 20 minutes? We definitely didn't drive thru, it was move - stop - move - stop and it sounded like hydraulics were in play, too. That's some amazing engineering in that video above.
Just my guess, but Switzerland has a lot of narrow gauge lines - due to the obvious terrain. These flex bogies make transitioning from standard gauge to narrow gauge a quicker process.
Rip track, there are a lot of metre gauge lines in Switzerland, some of them also see a level of traffic comparable to the standard gauge mainlines incuding freight traffic. As far as i understand this is to have a through train, and the Golden Pass is a kind of high end touristic train, so definitely worth the hassle and the investment.