Unfortunately the answer is no. Cellulose pulp, the main component of Murs d'Art together with the glassbubbles, is very sensitive in exteriors and most probably we would have a problem in just a few months.

Luciano,
Can you play around with the Prontomuro L and Aquarello? I would thing that you could lay out the stone with your tape and build up your plaster to get a rough stone look. (I may be way off base and if I am, someone correct me) It would obviously take more time and effort, but I bet a similar look could be achieved.

I was wrong (imagine that). I talked with Linda, she said you can play around with Immigini, the prontomuro will crack. She said that if you forget about the fact that the immigini is not Murs d'art, you can get a similar effect. I could only imagine that it would be worth it to knock out a sample board.
Later-