Reeves explained the new downward compatibility to PS2-Singstar titles in more detail. It will be realized with a software emulation which is contained in a coming firmware update. With this, all PS2-Singstar episodes would be directly playable on the PS3. There is no need for a PS3-Singstar. "We will observe for which titles this would also pay off, and in the future we will possibly get other PS2-games to run on PS3 by emulation." This is however a technically very complex process, since the necessary PS2-chips are missing in the current PS3-models."
I´m german and this translation is correct. So basically the only confirmed thing is that PS2-Singstar episodes will be "natively" playable on PS3 via firmware update, nothing more.
They might make other games playable as well, but this is just a possibility. There is no confirmation of any other titles at all. To state that this is fully backward compatibility is just nonsense.