for that, i know first 6gb PS3 can emulate PS2 games in hardware mode for PS3 40gb french, i have heard it's possible but in soft mode.
i have see many rumors that say a firmware have removed PS2 soft emulation for PS3 pal but i think it's unlikely. i have see on a web site about swap magic but i don't know what is the function and if it's emulate PS2.
I have the 60gb and haven't found a PS2 or PS1 game I can't play, I am glad I got full backwards compatibility and I wouldn't trade if for a 160gb, no doubt about it, Intelligent Qube and my PS2 games are worth it.
The first two models (20 and 60 GB) have hardware emulation i.e. play any ps1 ps2 game. Then 80 gb that followed had software emulation; i.e. play most games without a problem. All models after that removed it completely and can't play ps2 games, but I believe plays ps1 games. There is talk of a firmware update giving ps2 software emulation to all ps3s so they can sell ps2 games through the playstation store.
The CHECHA (60 GB) and CHECHB (20 GB) have hardware emulation. The CHECHE (80 GB) has software emulation. These are the ONLY MODELS out there in the US that supports PS2 formatted software and are NOT in production.