I was wondering the exact same thing today, you can see chimneys of the same type of construction on the south end of Caledonian Chambers as well You assume they know what they're doing, wonder what those chimneys actually connect to.What confuses me is those 'hanging chimneys' - they appear to belong to Caledonian Chambers as they are affixed to the adjacent building and are/were not part of the Union Corner building (as the rear part of the CC building uses exactly the same red brick).
Most Glaswegians of a certain age remember the animated IrnBru neon signage that stood bolted to the gable for many years, before latterly being replaced (I believe around 2010, firstly with a large format LED moving advertising display, before this too gave way to a full moving-video capable display in portait orientation from 2015.
It was hard to discern the mounting of it from ground level, but looking at the outline on the street-frontage chimney, this appeared to be a CC asset (before the flames from the Union Building totally overwhelmed it). Indeed, if you look carefully at the first video showing the smoke belching out of the Vape Shop, you can see the display glowing through the smoke and you can witness it extinguishing itself as it gives up the ghost. Its mountings have gone and there appears to be no evidence of it in the latest images.
Edit: I think there's a different building behind the Caledonian Chambers that it actually belongs to. It's definitely unstable either way


