The counters (I've checked the ones in Coin department stores in Venice and Florence) do not accept empties – no surprise there. However, I was able to B2M at the MAC store in Bologna and the MAC PRO in Milan. I didn't visit any other MAC stores (I believe it's just one more in Rome), but my guess is that it follows the same policy.
The majority of my empties were pots from depotted shadows (without the stickers at the bottom) and the MUA in both stores were completely fine with it – they didn't even look twice. They also do not have a limit on the number of empties you want to exchange (I had no problem returning 30 with a single purchase). The only downside is that – as in other European countries – you can only B2M for lipsticks from the permanent line (no LE even if it's in the regular black packaging, no glosses, e/s etc.).
I was surprised to find some discontinued products such as chartru paint, birchbark ccb, pink ccb etc. I was also impressed by the amount of LE items they receive – although In the Groove had been out for several weeks, all the stores and counters still had Stereo Rose (which is quite unthinkable to someone who is used to LE selling out in the matter of hours)! The prices are similar to German, but slightly steeper (approximately 1 Euro per product).