Section 139(1) of the HTA applies here.
139. (1) Every driver or street car operator entering a highway from a private road or driveway shall yield the right of way to all traffic approaching on the highway so closely that to enter would constitute an immediate hazard. R.S.O. 1990, c. H.8, s. 139 (1).
I can see the insurance company's point of view that both drivers should have yielded to each other, since the way was not clear (evidenced by the fact that there was a collision). Certainly if either driver had yielded, the other one would not have had to, but two wrongs don't make a right.
If one of the two vehicles was clearly in the roadway before the other one left the driveway, I would suggest that vehicle had the right of way. I don't know if that was the case in this situation.
The other thing to consider is that if a driver entered the road way and actually began to make a turn in one direction and then changed course to make a turn in another direction, 142(1) - Improper Turn - might apply.
142. (1) The driver or operator of a vehicle upon a highway before turning to the left or right at any intersection or into a private road or driveway or from one lane for traffic to another lane for traffic or to leave the roadway shall first see that the movement can be made in safety, and if the operation of any other vehicle may be affected by the movement shall give a signal plainly visible to the driver or operator of the other vehicle of the intention to make the movement. R.S.O. 1990, c. H.8, s. 142 (1).
I would suggest that Improper Turn doesn't apply when coming FROM a private drive onto the highway, however, if a vehicle was already on the highway, making a turn in one direction and then aborted that turn and made another (unsafe) turn in a different direction, then they were on the highway when they made the second turn and 142(1) applies. If the turn resulted in a collision they should be guilty of Improper Turn and at fault for the accident.
So obviously there are several different ways to look at it, depending on your point of view and how you articulate the actions of each driver. That being said, it doesn't really matter who's at fault under the HTA, insurance companies make their own determinations of fault, not necessarily in accordance with who has violated the HTA.
NOTHING I SAY ON HERE IS LEGAL ADVICE.