In their snooping around, it seems IGN has stumbled onto a PEGI rating for the original Deus Ex, which is slated for release on PS3. IGN speculates the game is likely the ported PS2 version intended for a PSN release, though they also say, "The release date for the new PS3 version is listed as May 1st..."
Unfortunately, the game no longer shows up on the PEGI website with the date listed by IGN. However, a screenshot of the rating can still be seen on the Siliconera website.
IGN rated the PS2 version of the game a 7.9. If this is the version we do see hit PSN, folks can expect "minor changes from the PC original, including new opening and closing cinematics, a simplified interface, and improved graphics."
Source: IGN, Siliconera