I was wondering the same thing. Found this thread. I'll keep digging.
I found this interesting write-up of a study comparing the growth of oyster mushrooms on Moso bamboo sawdust vs. conifer (Japanese cedar) sawdust. Both grown with either rice bran (RB) or Sweet Potato Schochu Lees (SPSL). They got some interesting results. Surprisingly, there is an abundance of this type of bamboo is certain places, as there is a much higher demand for the shoots than the rest of the plant. I'm not sure of the cost and availability over other substrates here in the West, but it certainly looks promising as a more ecologically-friendly alternative to using a hardwood.
Cultivation of oyster mushroom (Pleurotus ostrreatus) on fermented moso bamboo sawdust
"Shochu is a traditional Japanese distilled liquor, made by rice koji (Aspergillus kawachii), which is koji mould grown on rice grain. Rice koji is an essential ingredient of Japanese liquors such as shochu and plays as a source of enzyme to degrade starch... SPSL contain 1.4 times the nucleic acid-related substances of RB since it contains koji from shochu lees and yeast. BS which have been fermented for 2 months, contains microbe-derived nucleic acid substances, which seem to have shortened the growth."
"Conifer sawdust or broad-leaved tree sawdust is generally used for mushroom cultivations. Bamboo sawdust contains more nitrogen-free extracts (NFE) and less crude fiber compared to conifer sawdust. Based on the obtained results, bamboo sawdust with sweet potato shochu lees or mixture of rice bran shortened the total growth days by 3–7 days compared to the control group. Bamboo sawdust as the substitution for conifer sawdust did not affect the main components or the mineral compositions in the fruit bodies. The oyster mushrooms grown in the media with bamboo sawdust contained higher amount of free-amino acids than those from the control group of conifer sawdust. From these results, we concluded that bamboo sawdust can be used as the base material for the oyster mushroom cultivation. In future, the investigation of Moso bamboo sawdust could be applied in Malaysia, Thailand and Indonesia with their subtropical climate in order to extend their usage."