Can dual gauge be found in operation elsewhere?
It's mainly in Spain. In some cases it's transitional, but is there a serious plan to re-gauge all the "funny" gauge tracks?
Having said that - of course the Spanish have mainly gone for dual-gauge trains, if that's an OK term. There is some track there too, and bits elsewhere - I now recall seeing a little bit in France, at Tournon-sur-Rhone where the Chemin de Fer du Vivarais (T/A Le Train de l'Ardeche) runs up the main line for a bit.
As you'd expect, Wikipedia has a list of lots of examples, some very limited, and outside Europe there are some much bigger users.