Mom and Dad are travelling this winter, so I'm taking care of their cat, the Furred.
So the furred seems to be quite happy living in the shop. Mom was absolutely right that he likes sleeping on the pallet in the shop, and I built a little vapor-barrier plastic kitty door to fit in the window so he can come and go as he chooses.
I've been arranging hour-long sessions with him in the house, since it's got to be boring out there, but progress on having the cats get along has been slow. I've discovered our old cat (who I've provisionally renamed "Trout Cat" or TC due to his spots) can produce an alarmingly loud mountain lion-esque roar. It's pretty much that, or hissing, or silently stalking the Furred anytime he's in the house.
The Furred, for his part, has shown admirable restraint, and TC hasn't yet gotten the smackdown I suspect is coming if the provocations continue...