I filed a bug report on the same issue https://bugzilla.redhat.com/show_bug.cgi?id=968122
I am not an expert on Python or Anaconda, but it seems to me that the check arch.getPPCMacGen() == "NewWorld" is redundant because Fedora 19 PPC is 64-bit kernel only and all 64-bit PowerMacs are always based on New World architecture.
So really hope it is possible to change the following line in python-blivet platform.py
if (ppcMachine == "PMac" and arch.getPPCMacGen() == "NewWorld"):
if ppcMachine == "PMac":
in Fedora 19 PPC final release
Kinds regards / Met vriendelijke groet