DND is the top federal organization in terms of number of buildings and square footage; it's only third in land area - Parks Canada and Environment Canada have them beat. But still, the military is not a slouch when it comes to real estate holdings.
Granted most of that is used in support of full-time activities, but what about some of the expenses such as payment in lieu of taxation (PILT)
for facilities used primarily in support of "part-time soldering". I suppose I could have gone property by property to figure out DND's share of the $562,157,133.62 that the Canadian government shelled out in 2019 for PILT. However, I'll limit myself to a few examples, such as here in Calgary where the 2019 PILT expense for Mewata Armoury was $312,928.36, HMCS Tecumsah was $158,115.81, and the remaining Currie Barracks footprint comes in at $227,433.73; I don't know if the armoury in the NE is still being used but the City of Calgary received $147,765.61 from DND's budget in 2019.
It would be nice to have the wide open space of a re-purposed mall or similar commercial/industrial structure (I think that was the background of the armoury in NE Calgary) but how much of it would actually be "efficiently" utilized for one evening a week and one or two weekends a month for nine or ten months a year. There's a not insignificant cost to that footprint.