Interesting read, thanks.
The article is a little misleading. There has been a small population decline in Chicago proper, but the overall metropolitan area has continued to grow quite consistently. Chicago is merely experiencing what has been occuring for decades now: urban flight. Suburbanization and sprawl persist at the expense of inner city areas. Unlike Montreal, Chicago is not on an island. Large freeways with many lanes exist all over the place, and the city is far more automobile-oriented than Montreal is. It's easier to drive around, hence, people opt for cars, which leads to demand for car-oriented development (i.e. suburban housing), which leads to growth in the suburbs at the expense of the city itself.
To sustain the creative class and attract new investment, Montreal and Chicago need to intensify their urban activities. In order to do that, they need to stop sprawl, improve their transit systems and focus on in-fill development, densification, walkability, etc. Doing this alone will save hundreds of millions of dollars. To increase revenues even further, gasoline taxes should be raised. Gasoline taxes haven't been raised much over the last few decades, and as a result, they're the lowest they've ever been, accounting for inflation. The taxes haven't kept up, and today they don't even come close to covering the infrastructure maintenance costs associated with roads, let alone their implicit negative externalities.