What province are you in? Here in Alberta, I inquired about using a rock truck for hauling dirt and manure. As it turns out, they are now road legal in Alberta. Meaning that they need to be registered and insured. Lights and brakes etc need to work. I assume the driver would need to have air brakes and a license. And that they would have to meet legal axle weight limits, but I couldn't get an answer about what that weight is.
Using a trailer behind a tractor would be a grey area. I'm told the definition of farm machinery is that it had to start out its life a farm machinery. Therefore repurposed construction equipment does not qualify as farm equipment, so the trailer may not be legal if push comes to shove.