http://www.e-laws.gov.on.ca/html/statutes/english/elaws_statutes_90h08_e.htm#BK165 (see the definitions in the beginning, and also section 103.1)
Now, follow me for a moment ...
The device in question is a "motor assisted bicycle". Doesn't have to be electric to fit this definition - it doesn't matter at this line in the definitions.
The definition of "motor vehicle" includes "motor assisted bicycle unless otherwise indicated in this Act" but it excludes "power assisted bicycle".
The term "power assisted bicycle" doesn't do you any good because it has to be in compliance with the Motor Vehicle Safety Regulations (this is where the e-bikes fit into). A home-built contraption has no such (legal) label and declaration.
So, that means it is a "motor vehicle".
And that means it is subject to EVERY requirement in the HTA that applies to a "motor vehicle". License plate, vehicle registration documents, insurance, lighting, etc.
And you can't get that license plate and registration documentation for something that doesn't have a (legal) VIN.
And you can't get a VIN for a bicycle with an engine on it ...