France is one of the countries in Europe where the 900 MHz band has been opened up for technologies other than GSM and where a 3G network operator has started deploying UMTS 900. Some UMTS 900 / 2100 MHz USB sticks have been available for a while and especially Nokia puts UMTS 900 MHz into a number of its higher end devices in addition to the standard 2100 MHz band support. Here's a link to the coverage map of Orange France that shows which areas are covered with the standard 2100 MHz UMTS band and which are covered with UMTS 900.
It's interesting to compare those maps with satellite maps to see what kind of areas are covered with UMTS 900. It's very rural areas indeed so it looks like Orange sees a business case for covering such sparsely populated areas with a frequency band on which the signal can travel much farther than on 2.1 GHz. Also, it proves my assumption that especially in rural areas, there is enough bandwidth available to run both GSM and UMTS alongside each other, have enough bandwidth for GSM voice and data and still enough space between the technologies to keep the interference between the technologies on the air interface in check.