Actually, Metrolinx has already disclosed the type of electrification in their documentation.
https://assets.metrolinx.com/image/upload/v1737998921/Documents/Engineering/CPG_Performance_Specifications_for_ET_EW.pdf

Section 1.2

« The Metrolinx Electrification system shall be a 2 x 25 kV ac (1 x 25 kV ac in the limits of the Pearson 
subdivision), 60 Hz autotransformer traction electrification system. »