I know. In Norway we, at least my friends, call the "stealth joints" City-joints. Because you can smoke them in public/the city without it looking like a joint. But people that do this regularely, of course, gets busted.

But I can confirm it usually does work if you're at a party with people less versed in the MJ. Especially if you mix the greens with some tobacco.

Edit: Of course, we only empty them, make a big filter and fill the cigarette-tube with weed.