Nice pic Jack!
The local open space authority has been doing a similar thing on the ridge across from our place every year for the last three years (actually didn't do it last year, because of conditions).
The original intention was to try erradicating Yellow Star Thistle (YST, the scourge of the West). Very successful the first year. The first year they burned 80 acres, and only 5% of the acreage re-sprouted with YST. It was so successful, they expanded the acreage to 160 acres the second year. Third year they didn't burn because the conditions didn't meet the "prescription".
They call it a "prescribed burn", not a "controlled burn", because there's no such thing as "controlled" when it comes to burning. The term "prescription" more closely describes the process: there is a "prescribed" parameter for several metrics including wind, soil moisture, plant moisture, relative humidity, temperature, and so on. If all the parameters match the "prescription", they do the burn. If not, they don't.
The GlueGuy