We call them "hydro towers" in Northwestern Ontario. They're also referred to as hydro towers in the opening line of the song "Shine" by Hamilton, Ontario band Junkhouse.
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"We live around the hydro towers
Listen to them singing in the park"
That song is 19 years old now.
Hydro One calls them "Transmission Lines". They don't make any specific reference to the towers since they're just holding up the lines.