No, he's actually right in many places.You must be measuring with Imperial metres.
In the central and west end of Toronto until the corridor crosses just west of the 400, the hydro corridor is closer to Finch - as close as about 210m in some places, but generally closer to or slightly over 300m from the north sidewalk to the southern edge of the corridor. (If the northern portion of the corridor was used, than obviously the distance from Finch would be correspondingly larger as well.)
(Which also raises a question that I've not seen effectively answered by anyone who offers the corridor as a viable transit avenue - what do you do west of the 400, when the hydro corridor ceases to be an option?)
But east of Victoria Park? It's at or over 1000m from the north sidewalk to the southern edge of the corridor.