One for the pot.
There is a long narrow building amongst the farm buildings at Knockaloe that was (is) known as the engine shed.
I remember looking at the first few rafters back from the door and noticing them being being higher than most of the rest. Although this suggests accomodation for a locomotive, the construction is the same at the other, western, end. Annecdotal evidence was that , despite the name, the shed was never used to house an engine.
As the editor is want to suggest; Discuss.

The site had a power house /engine shed used to supply electricity, which was probably this building.  The higher rafters could be to house a boiler.  The building's roof is clearly not original, so it's hard to tell if had a chimney or suitable vents in the roof to steam a locomotive.

Personally, I can't see the reason to house a locomotive on the site and you would need a water tank at the very least.  It was more likely that the 'Cale' was kept at Peel as most of the traffic for Knockaloe arrived at Peel.  Possibly, the Peel engine shed extension was for this very reason to house the 'Cale' - it looked originally only temporary and hastily constructed (date erected?).   

Although, never say never, and it would be nice to find out if it was a shed to house a locomotive.  Maybe, one day, somebody will find an old photograph in their attic.

JIC Boyd in his history of the IMR refers to the shed in volume 3.  He states that although shown on the plans of the camp circa 1915 it is NOT shown as rail connected.  Are there photographs that actually show it ever being rail connected? He thinks that it was used to store farm implements.  The roof trusses at the east end were modified to provide more clearance, but was this for Caledonia or some piece of farm machinery?