CAR does have something related to conference usage, but I don't think you will find it useful. You could check though if you want.
I actually went through this exercise many moons ago. I found that the best thing to do was to pull the data from the CDRs and just process it to determine the average users, hold times, and volume of calls. Since you are talking meetme conferences, you will be able to pull this information from the CDRs.
HTH.
Regards,
Bill