Rear Fog lights
 

Is there a way in the US to purchase and fit the rear foglights that the European E70's have as standard?

NO

In theory its possible, I know people have done it on their E46's
they have gotten a european version of light switch module with has a rear fog button added, basically on E46 front fogs button is split in two for european version. I doubt that all additional wiring is in place, so that probably has to be ran, I am also almost sure you would need to replace tail lights to have a socket for fog bulbs.....

Is it worth the hassle???

I doubt it!!!
With cost and effort spent to add this feature, its really not worth in US market, people here dont understand rear fogs and some dont even know when and how to use them. I had seen some people in Jag's, MB and some other cars with rear fog lights driving around in normal weather and its pretty annoying to follow a car with such bright "TAIL LIGHTS"

It's a bummer, as it is definitely a safety factor here in Colorado with blizzards etc. I wonder why BMW don't allow them here. We have bad weather too and should have the chance to prevent accidents like Europeans do too.

It is like the stupid attorney warning in the IDrive that you have to accept to speed up access to the rear view camera. I think it is dangerous being forced to accept these stupid attorney disclosures, the backup camera should just come on!