From vague, vague memory, I seem to recall something in the HTA stating that the headlights of a vehicle must fall within a certain height, and I could be way off on this one, but I think the maximum could have been 120cm.
I remember this being brought up in a debate over lifted 4x4's blinding people... and there was also a reference made to those 'headlight relocation' kits that move the truck's OEM lighting down into the bumper.
Edit: Wow, should have read the OHTA before posting. I could be thinking of the Alta HTA. Just went through the lamps section and found no such restrictions on height, could only find this restriction on the number of lights:
Quote:Strength of front lamps
(9) No motor vehicle shall carry on the front thereof more than four lighted lamps that project a beam having an intensity of over 300 candela. R.S.O. 1990, c. H.8, s. 62 (9).