Bike lanes on a traffic circle seem pointless. The whole idea of a traffic circle is that it accomodates an arbitrary number of entrance and exit points, and any bike or car may need to use any of them. So where would the bike lane direct the bicyclist?
In the LAB Road I course I took, we actually navigated a traffic circle during class. The instructor had us enter the circle one at a time, ride completely around a few times on the inside lane, taking the lane, then exit to come back. The point being that unless you're getting off at the very next exit after you get on, you're better off moving to the inside lane until you're approaching your exit, then negotiate to move back outside and off. The cars are usually not going all that fast in a traffic circle (unless it's a very large one), and on the inside lane, you don't have to deal with people entering and exiting the circle at every single entrance you pass. This advantage would seem to be completely negated by having a bike lane that simply follows the outside of the circle! (Assuming that's where it is.)
Riding the inside lane not only cuts down on your interactions with cars at every entrance/exit point, but if you can't successfully negotiate when you need to move to your exit, you can easily just go around again and try next time!