The thing about a study like this is that it doesn't really need a qualifier. They showed that there is a correlation between bike lanes and bike commuters. They showed that this correlation held true despite weather and a number of other co-factors.
Maybe promoting the bike lanes helps. Maybe people use bike lanes even if they aren't promoted. That wasn't part of this study.
It might seem obvious, but this is a really important study. It seems obvious to us but go to a city council meeting and propose bike lanes to encourage bicycling and someone will inevitably say, "Well, we can build all the bike lanes and bike paths we want, and no one is going to use them." Or they say, "We built a bike path in 1972, and no one uses it" (referring to a 0.5-mile segment of crumbling asphalt that goes from nowhere to nowhere).
We have to have data to make a case.
I looked at the original study. They got their data from the Census, the Bike League, and the Alliance. I am intrigued and thinking about the possibilities in research. (First thing to do is probably remind myself that this is not my field. This isn't the type of research I do. I am not trained in this type of research. I have a day job where I'm paid to do a different kind of research. Too bad I rarely listen to myself...)
2009 Trek 7.2FX WSD, brooks Champion Flyer S, commuter bike