A friend did some research this past spring that involved Ontario
Hydro records. I asked him for some details.
Ontario Power Generation holds the Ontario Hydro files that he looked
at. They (the records) used to be held in their main building on
University Ave, but they have been relocating and culling them over
the past decade. He had to go through an Access to Information Request
to look at the files. After it was granted he was directed to the OPG
facility on Kipling. It sounds like they have very few external,
non-OPG researchers visit and records were poorly organized,
identified, described.
I can provide you with a few more details about his visit offline. I
don't have any information on the specifics asked about at the
beginning of this thread.