...and they asked these barbarians about whisky?!
I have never heard of anybody here in Scotland drinking whisky mixed with Irn-Bru, except as a dare. Expensive whisky is drunk neat, or with a bit of water; never with ice. Increasingly, nowadays, you get whisky cocktails. Cheap blended whisky is also drunk neat, or with beer (either side-by-side or as a boilermaker, with the shotglass of whisky dropped into a pint of beer), or with soda water or lemonade.
Irn-Bru is usually drunk with vodka.
Edit: by a few years I mean the late 90s. Getting old.
This is the beverage equivalent of a dry-aged, marbled, fine Wagyu steak cooked to a perfect medium, then covering it in ketchup. Sacrilege.