I've never heard of any prohibitions on having cameras in office spaces... our restaurant chain client has a camera in the office in every site, as well as in the "open" staff areas (both to watch for theft from employees, and to keep tabs on their cash-out areas). Many sites have cameras in places like staff lunch rooms as well. Unless there's a "reasonable expectation of privacy" (washrooms, etc.) there's no reason I know of that a site wouldn't be allowed to have cameras.
My experience with professional buildings, landlords or property managers wouldn't go to the expense of putting cameras into tenant spaces... and I doubt most tenants would want building management snooping on their businesses. Plus these spaces are usually renovated to some degree between tenants, which may include moving of walls, and/or shuffling of ceiling tiles to alter lighting, etc., which would lead to cameras being moved, re-oriented, or blocked - there's just no point. Management would only have cameras in the common areas, like hallways, building lobbies, parking garages, etc.
No, in a site like this, the cameras within a rental space are almost certainly installed by the tenant... although in Canada at least, I believe the space is leased by a non-partisan government agency and is occupied on a rotating basis by whatever elected party representative is in it for that term. As such, there would be little physical change to the office on a regular basis, other than things like decor and furnishings.
In any case, I doubt it could be said the people in the video didn't know there was a camera there. It's obviously an IR camera, so probably not anything covert. More likely, as we've seen and discussed elsewhere, they're simply oblivious to it as they would be to any other ceiling fixture.