This is a bug for somebody to evaluate the work that needs to be done in preparation for btrfs becoming the default fs and then start working towards getting changes into btrfs to make it work properly with livecd-tools.
This bug appears to have been reported against 'rawhide' during the Fedora 19 development cycle. Changing version to '19'. (As we did not run this process for some time, it could affect also pre-Fedora 19 development cycle bugs. We are very sorry. It will help us with cleanup during Fedora 19 End Of Life. Thank you.) More information and reason for this action is here: https://fedoraproject.org/wiki/BugZappers/HouseKeeping/Fedora19
I don't see any reason for the iso filesystem to be btrfs now that anaconda can install to any filesystem you choose on the target system.