I admit that it does seem pretty strange at first, but let's face it, most of the pleasant land (along the Ottawa River) already has a pseudo-expressway on it already. And if this is combined with an LRT project (which is already facing significant opposition), it'll be more likely that both get built.
The lands that it's running through are pretty dead in terms of any kind of park and pedestrian use. There's a couple bike paths through it, but that's about it. It's far from being prime parkland.
And when compared to widening the 417, which would require the expropriation of countless properties, and cost likely in the billions of dollars, running a new road through underused open space doesn't really seem that bad.
Plus, the main entrance way for tourists by car into Ottawa is via the 416. How nice would it be to have them end at the 417, take that for an exit or two, and then get off directly onto the ORP, so that one of their 1st experiences of Ottawa is a great view of the river, as opposed to a utilitarian expressway? That's one of the things that I love about the DVP: you come around the corner at Spanbridge, and BAM, there's the city. Although using the ORP would be far more calming, haha.
