On a recent trip to Boston, I saw this generous bike parking shelter, with card-controlled door:
And while on that same trip to Boston, I stayed in a hotel built on air rights over a commuter rail line and freeway. The hotel windows were thick, and sealed. Noise intrusion was minimal and I slept fine. For one night, OK; but I wouldn’t want to live above the freeway or rail line.
At the present time, there are no intentions of selling or leasing air rights over any of the Ottawa’s new LRT lines, as the additional construction cost doesn’t warrant competing for that land — yet. It would make it easier to build on the air rights some day if the two tracks were separated a few feet, to allow for building support pillars, but we don’t plan to do that, even in high value locations, or for lower-value buildings like garages.
I think the ~4 lane span on the left in your example is wider than the LRT span will be even without spacing between the lrt lanes.
It is not a question of what is technically feasible, it is a question of economics. Building pillars are usually about 18′ apart. Over the freeway, or a pair of rail tracks, the pillars are further apart, so a very heavy horizontal beam is required, which becomes the new foundation for the regularly spaced pillars above. This heavy beam is expensive and its thickness is an issue. If the two tracks are separated a few feet, then pillars remain 18′ apart and the building is cheaper to build. Pillars are not acceptable between road lanes.