From a CBC article:
"Guinan's team of five glaziers at Toronto company EGD Glass are sharing the job of fixing the windows with another restoration firm, Vitreous Glass. They scrub away the dirt, replace cracked glass, and touch up blemishes on the composers' faces, in an effort to rescue the 93 historic windows.
It's part of Massey's two-year "revitalization" project, valued at $139 million and set to be completed in late 2020, that will inject new life into the venue."