Spot checks are carried out all the time throughout Turkey. Unlike the UK, the Turkish Polis and Jandarma don't need reasonable cause, they just set-up roadblocks and get on with it.
I had a bit of a scare one night on the way back from Sivas. My mate Bill was driving my truck and we were pulled-up at a roadside check near Konya. The officer asked for our papers and the documents for the truck. He then said that I had to go with him to his car, where I was promptly breathalysed. Neither of us had had a drink in the past 24 hours but I always wonder what would have happened if I'd given a positive reading even though I wasn't the driver at the time.