The OPA has been directed to run an RFQ for energy storage. One of the main issues is the compensaton and wh gets to keep the value that energy storage provides the system. There currently are 2 pilots systems up and running in Ontario. Compressed Air Energy Storage has also been proposed but the above issues, dispatch and cost have inhibited its adoption in Ontario
http://www.powerauthority.on.ca/generation-procurement/energy-storage
should be interesting to see what the new recombined IESO/OPA organization does in the new year.