It’s no longer just a research trend. Now most of the big companies are turning “green” using CO2 exhaust reductions as a heavy argument in their advertising of their products. Check out this site (and video) as an examples (NokiaSiemens) http://www.nokiasiemensnetworks.com/portfolio/services/energysolutions
Ericsson launched a line of low-energy basstations (the “funnels”) late 2007 . but not much noise about this since.
The GSM community recently published its
Mobile’s Green Manifesto