When in Doubt, Back Out
Twice in the past week I've watched drivers who were stopped legally in the intersection signaling a left turn back out of the intersection when the traffic light that they were facing turned red. Why would a driver do this? The action is completely out of context and unsafe.
In this situation, surrounding traffic is not expecting these drivers to suddenly reverse. They will either pull directly up to the stop line or may even attempt to follow the left turn vehicle through on the red. At best there is no room to back into, interfering with cross traffic and at worst a collision will result.
In British Columbia it is not legal to move backwards over a crosswalk. This rule almost certainly prohibits backing out of an intersection in urban locations. Remember that a crosswalk does not have to be marked with paint on the roadway to exist.
These drivers had the right of way, once the signal they were facing turned red, to complete their left turn safely. Cross traffic cannot legally enter on the green until the left turn vehicle exits the intersection. Backing out of the situation is not the correct choice.