Opium isn't typically "smoked" in the same way weed or hash can be. Opium works best when vaporized. If you were to try to burn and smoke it through a joint/bong/weed pipe, it's debatable how well it would work, but it would be very wasteful at least.
Opium is pretty rare and more expensive than weed/hash, as far as I know. I don't see a reason why coffee shops would give their customers free opium; especially when the customers wouldn't be aware of it or consume it effectively.
https://en.wikipedia.org/wiki/Opium#Consumption
https://en.wikipedia.org/wiki/Opium_pipe
There do seem to be some accounts of this online though. This article seems to suggest it's pretty common, but after a quick read through it's pretty misinformed on some stuff:
http://www.hiptravelguide.com/guides/modules.php?name=News&file=article&id=309&site=1
Maybe it is available, but I'm pretty sure you'd be told by the seller what exactly you were buying and you'd be paying substantially more.
http://bluelight.org/vb/threads/452014-Opiated-Hash-How-common-is-it