Typically office building parking is operated as a commercial garage which allows for visitor use, the fencing must be a temporary measure in preparation of the garage's opening.
It's not uncommon for visitor parking these days downtown to be bundled up and sold off for commercial operations - as long as the parking is publicly accessible it still qualifies for the visitor parking requirement.
My building expanded the visitor parking area into residential section after opening, to give more spaces since it was in such high demand. The building is built to by-law parking rates, so 0.1 visitor spaces a unit and ~0.5 residential spaces a unit, but the 0.1 wasn't enough visitor, it's probably closer to 0.15 now. The residential demand is probably closer to 0.25 by the looks of it, so the garage is pretty empty.
Mind you it's a rental building so it's not like the residential parking is individually owned making it much easier to do the conversion, and while the visitor parking isn't free, it's about 1/3rd the price of market pricing in the area, so people tend to use it at really high rates.
I'm not that big a fan of very low visitor parking ratios as it is one variable that tends to stay relatively high in demand regardless of how urban a location is. Residents can easily live car free - but visitors often come from not so urban locations and need places to park.