What you posted what about Mycorrhizae. Which is Greek for Fungus Root, however, I can assure you from using plenty of Mycorrhizae that I have never had mushrooms growing out of my mediums.
The spores/fungus they use in Mycorrhizae products are not the same as a typical mushroom style fungus. The mushroom is the actual "fruit" of the fungus which is a different species then what is used in Mycorrhizae products.
I haven't seen any studies or information pertaining to fruiting style fungi used in the root systems of marijuana plants. Furthermore it would stand to reason that a fruiting style fungi would eat more nutrients out of the medium possibly even starving the plants for nutrients, as that can even sometimes happen with non fruiting species of fungi.