Altitudes do not need to be corrected until 0 degrees C. Above that any difference from standard is negligible (at Sea Level). Indeed, down to about -5*C the difference is not that much. For higher altitudes, the difference can become quite drastic.
Here in Canada with a similar SID or STAR that you've show (say, the ones coming into Calgary from the West), ATC will simply amend the altitude on the day. They'll give you a higher clearance limit, normally with the phrase "altitude restrictions cancelled, climb/descend FLxxx/xx,xxx."
So in Milan on a very cold day, ATC may amend the clearance to FL150 if they think temperature will be an issue...but then, how many days a year does Milan get below 0*C to the point where ATC would have to think about higher altitude corrections?