Bikram Yoga people often claim that Bikram Yoga burns more caloreis than running. I have never seen anything to support this, except for occassional comments on using a heart rate monitor to validate the calculation. Unfortunately, Bikram Yoga does not meet the typcial expectation for the math behind heart monitor calculations. Also the Heart rate is greatly increased due to the heat of the room, not due to the exercise.
If it were me, I would treat it as yoga, you may under represent the workout slightly, but this will not be an earth shatering amount in my opinion.
I would rather error on the side of conservativeness than think I am burnning way more calories.
Please note, I am a runner, tai chi chuan player, Qigong practitioner and Gramie does yoga most days. We are therefore very positive for things like yoga, taiji, etc. but I like to be clear what they are, what they are not, and that people have realistic ideas about what they offer and what they do not.