The city's current light-rail transit plan has, since its inception, pencilled in the western corridor of the line to run along the NCC-owned Ottawa River Parkway. Despite obvious reluctance on the part of the NCC to allow the line, it's continued on as the default option, even while the city investigates the feasibility of other western-corridor options, including Carling and Byron.
It seems that city staff and planners are reluctant to face an obvious fact: The Parkway option is simply not going to happen.
The NCC is obviously no in favour of the option. Since the plan was approved, the NCC has been telling the city that they'd better investigate every other option available, because they'd need a compelling case to offer the Parkway for light-rail. Although they haven't said so explicitly, they've hinted as recently as last week that they're not convinced.
The Parkway option would have advantages. It's the simplest because there's little development to disrupt; it's the cheapest for the same reason; and it's the current western corridor so there's an ease of transition. (It would also offer riders a pretty sweet view across the river as they ride the train, but that's probably not a deciding factor in the debate.)
But those advantages are based on a fact that is also the most significant criticism of the option: Namely, that it's not surrounded by high populations. It would draw well from the northern portion of Westboro, but on the other side is just a river--not many people live in there. Contrast that with Carling or Byron, which are surrounded on both sides by fairly high-density residential areas as well as retail sites and plenty of employers.
Last week, David Reevely blogged about a letter from the NCC to the city in which their tone changed slightly: They don't want to allow trains on the Parkway, and they see little reason to think that would change.
I'm sure few would argue that using the Ottawa River Parkway land as a scenic roadway is the best use of that land, but using it as a light-rail throughfare wouldn't be much better.