The Canadian site seems to be quite dry. There is about one half metre of precipitation in the year and about one third of that is snow. The boreholes are in a circle about 35 metres across and similar depth with just the top covered and insulated. The hotter boreholes are in the centre so the clay and rock acts as a horizontal insulator. Clay is a good insulator when dry and useless when wet. They lose about half of the heat stores and I would suspect that much of this is when the snow melts in the spring when the stored heat is at the lowest level. Obviously in areas that don't have -30c surface temperatures in winter the situation is much different because the rain constantly penetrates in the winter. I am not very familiar with western Canada but my grand uncle Joeseph Keele surveyed large areas of north west Canada and has a river and mountain named after him.
What it boils down to is that the underground situation determines whether it is worth trying to store heat underground but in any case it needs to be concentrated and not spread out like a normla ground source loop.
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