Well, the permaculture experiments are happening on my farm (which is somewhere around 10 acres if I do the conversion properly). I don't really have much outdoor property in the city, just a courtyard and a small front lawn.

The high tunnels are closed off in the cooler months. The picture has them opened to vent because it gets too hot otherwise. There is anywhere between a 5 and 10 degree (Celsius!) difference between the inside and outside of a closed high tunnel. Add a similar difference with the low tunnel (and they stack!) so that when it is -20C outside, it could be as warm as 0C (freezing, but just) where the plants are growing.

In the low tunnels on that picture, it looks more like the plants are just growing out of the tunnel. It should pretty much go down all the way to the ground, and any plant that isn't on the inside just doesn't get the benefits of the low cover (greater moisture retention, higher temperatures, more frost resistance).

As far as watering goes... at a certain point I just stop watering. As the season gets colder, the plants slow and then stop growing (as you mentioned already :) ) at which point they don't less and less (and ultimately no) water.

As for freezing and tomatoes... frost will damage them pretty badly. It is like frostburn on humans. All the tomatoes that I had left outside have blotches of frostburn on them. They will spoil faster and that part needs to be cut off for the tomato to be used. Makes me very grumpy! We shouldn't have frost in summer!