I've wondered this myself. I didn't think sod would send roots down while it's dormant... ]
Local high school just a couple blocks from me had sod laid, a LOT of it in mid december. followed by NO water for 2 or 3 weeks. I saw one one warm day a few weeks back they had the irrigation on, but there looked to be broken lines or missing heads as the water was just flowing out of the ground by the sidewalk near the road for several hours. Go low bidder!
I'm curious to see the outcome in april. I don't think it's going to matter much, they won't care for it anyway. What was laid last summer half died by fall because of too much water, than not enough, then letting it get a foot tall before mowing, then cutting at like 2". What a huge waste of MY money!!!