It seems that you have two questions. If I understand your post correctly, your first question could be posed as follows:
"Is it possible that my 2.79M walk burns the same amount of calories as my 40min cardio routine?"
Answer: Not likely. The link that you provided in your question shows a workout routine that is much higher intensity than just walking. And, given that the two activities are approximately the same duration, the higher intensity routine will burn more calories.
My recommendation on what you actually do is based on your stated goal of losing fat. First, I have to correct your assumption that "a burned calorie is a burned calorie." This is NOT true.
At higher intensities, your body metabolizes a higher percentage of carbohydrates to generate energy. At lower intensities, your body metabolizes fat at a higher percentage to generate energy. The ideal intensity at which to "burn fat" is in Heart Rate Zone 2.
Therefore, my recommendation is that you neither walk to work or do the cardio kick boxing. Instead, I would recommend jogging easy to work and toweling off when you get there.
