Follow the money
Let's run the numbers. According to Wikipedia (http://en.wikipedia.org/wiki/Shams_solar_power_station) the plant will supply power to 20,000 homes. Total cost to build it is US$600 million.
600M/20K = 30K USD per home, just to cover the startup costs. Seems pretty pricey, particularly considering the very cheap land and blazing sunlight available. Over the 25 year life of the plant, I would suppose the running costs would possibly equal the build costs (guessing here), so they need to recoup at least 2400 USD per year per home, under ideal conditions (yeah right). Clearly this won't happen without subsidies.
And apparently a big chunk of the required tax subsidies are coming out of the pockets of Europeans?! Sounds like a sweet deal for those 20,000 homeowners...