I had to figure all this out this past Summer. So, to summarize and confuse the above, in Ontario:
- You can drive a single-person, 4-wheels on the road, plated, registered, and insured, if you have a car DL,
- If your township has a bylaw permitting their use on secondary roads (not County roads, which sucks, as I have 300m of county road to get to miles of secondary),
- you cannot have a passenger on board while on the roads, or while crossing the roads,
- factory-designed two-ups, with linger wheelbases, and much safer than DIY 2-ups, are not permitted on roads due to my first point (the laws will catch up, but very slowly)
- No UTVs on roads
Check your bylaws - around me, I can ride on the secondary roads until official dark (sunset + 30 minutes), which sounds reasonable until you realize that you'd actually be hunting until seconds before that (enough time to unload and sock your firearm), so if you arrived by ATV, the b@stards are stealing the best last minutes of the hunt from you, by making you get home before last light.
The 2-up seats are legal to own (if not on private land, check the trail operator, etc, regs), though nobody will recommend them (I've got one), just be aware that the centre of balance is far rearward with a second adult, so no hills, and watch the acceleration, as you should be golden.
On crown land, if on a trail organization's trail, you must have a trail pass UNLESS you're hunting (that land is shared, and hunters have a right to hunt, just as the trail clubs have a right to put a trail in). So, the 3-4 times a yea I'm out there, I have a shotgun in the scabbard, rather than pay the huge trail permit (of course, if I ever catch the trail-riding bug, I'll certainly get a permit.