Actually, I didn't write zero, I wrote less than zero and I even bolded it, so hopefully the message would get across. Lets see "how it works" - the landlord still has to pay all the building costs related to the empty space. So, to clarify it is a negative return (ie. zero revenue less costs). Empty space still has to be heated, lenders still want interest, whether the space is occupied or not, there are security costs, etc ....
Now perhaps some those pension funds don't pay that close attention to how their properties are managed, or those in Edmonton are not as evident to them as in other places where commercial rental has been much more robust over the last decade or so.
It seems to me some spaces here have sat empty 3 to 5 years or longer, so all those carrying costs have to add up. At some point expecting a mythical tenant to come in and pay premium rates in a tough market is really faint hope so it is unlikely you will come out ahead after being in the hole for several years. I think that's how it works.