I'll poke Richard abut this, as for now: Either find a new PPA, or you could try to use the unstable cantor builds from Project Neon. (Add ppa:neon/ppa and install project-neon-cantor, it'll be installed in /opt/project-neon/bin/cantor). We build with R enabled, but since we give no guarantee that it'll work it's not a permanent solution.
The MIR was/is bug 497158 btw.
Ubuntu Bug Squad volunteer triager