For normal home waterpipes its better with flow water in the winter as a ice protection.
But the garden pipes for the sprinkler have normaly a dryout valve. To help do dry the pipe if there is no pressure on it.
Looks like this: http://www.brianzaremba.de/DasProjekt/GartenFit/GartenFit_017.jpg
The risk of broken pipes would be higher, if you watering your system under 0 degress.
I know some days last year we have one day 10 degress. And at the next day we have to search for your cars under the snow. 🙂