I'm sure most engineers have been wondering whether their Zapthrottle Mote Extractor would still be useful in the expansion. I wondered this as well because my engineer relies on it quite heavily to provide her an income source. When I first arrived in the Beta, I didn't see any cloud formations in the zones I visited. A few builds later I spotted some things which could possibly have been cloudy. So I eventually grabbed my tank and went out to investigate.
In the Borean Tundra and Sholazar Basin, there are windy clouds called 'steam clouds' which contain crystallized fire and crystallized water. In Howling Fjord you can find solid looking objects called 'arctic clouds' from which you can extract crystallized water and crystallized air. As you may have guessed, these clouds work differently than our current clouds. For one thing, all clouds are a source to more than one type of element. Arctic clouds usually don't offer both types of element from the same extraction, but steam clouds can.
Also, some of the new clouds seem to be more regional in nature. For arctic and the Borean Tundra steam clouds, you're unlikely to find them over land. They're predominantly concentrated in water-covered locations. The windy clouds in Sholazar Basin are similar to Nagrand in that they are randomly located and terrain doesn't seem to be a variable.
That's all I know so far, my engineer isn't really high enough to fully explore every zone. The important thing is that there are clouds in Northrend and your mote extractor works on them. So keep your eyes peeled when you arrive and don't leave home without the hardware!
On a different note: the robotic mobs in the Scalding Pools can be mined by Engineers. Usually they drop vendor junk, but occasionally they drop useful engineering parts :)