The paper (http://ftp.iza.org/dp1278.pdf) does not mention cars, bicycles, walking or any other means of transportation. It only says at one point that one of the factors which can make commuting stressful are congestions (and it uses the word "driving" there).

The paper analyzes the trade-off between having a longer commute (= more stress) and having a better-paying job (= less stress). This is a trade-off because you can get a better job if you're prepared to commute farther.

They are then quantifying that trade-off based on various statistics, and in a footnote, claim that it takes a 40% higher salary to compensate the stress caused by an 1-hour commute. It does not relate this to the type of transportation used.

The ecovelo blog then draws a bunch of pro-cycling conclusions from this, but they are their conclusions. They are not in the paper, and unless ecovelo knows something I don't, they're pulled out of thin air.