There is a bit of a surprise hidden in the PS4 bundles that include Star Wars Battlefront. Sony are listing the contents of the bundle to "include a voucher containing four Star Wars Classics".
Further examination reveals that these classics are games called Super Star Wars, Star Wars: Racer Revenge, Star Wars: Jedi Starfighter and Star Wars Bounty Hunter. The first one of these was released on Super Nintendo, but the rest of them were seen on PS2. So these games are the first proof of PS2's emulator at work on PS4.
Digital Foundry has done some tests on these games. They seem to be running around 4X the resolution of the originals, and include some post-processing effects to simulate anti-aliasing. Plus the frame-rate has improved substantially, as Jedi Starfighter hits 60fps.