I've read section 148/149 but I am still uncertain in this case. Can you legally pass a passing vehicle if all lines are broken and you can see it is clear and safe to do so?

I've added a visual for understanding. Truck B is passing Truck C. Is it illegal for Car A to pass Truck B while he is passing Truck C if Car A can see the way is clear of oncoming traffic and no cross roads??? Car A and Truck B are both using oncoming lanes to pass as there are two lanes heading one direction and only one lane in their travelling direction.

The lines painted on the ground are meaningless, unless there is a sign that says do not pass

However, if a collision occurs... it's covered in the Fault Determination Rules: http://www.e-laws.gov.on.ca/html/regs/e ... 0668_e.htm