A temporary truce between unions may have let opening night at La Scala proceed as scheduled, but that doesn’t mean it went smoothly. A gale of boos and catcalls landed on Daniele Gatti, apparently for his decision to replace the lead tenor 24 hours before curtain. Several of the singers received very mixed reactions from the crowd as well. In keeping with longstanding tradition, this major occasion on the Italian artistic and social calendar featured myriad protests on the plaza in front of the opera house; inside, there was another shocker as society’s grande dames admitted to wearing gowns that weren’t new.