There is a lack of focus on public transportation and rail transport in order to take trucks off the road. That, combined with the requirement to commute long distances (from a functional perspective) means the highways/roads are overfull. From my understanding, there is no competing highway allowed to be built along where the 407 corridor as well, so that's not a possibility.
In order to make a reasonable impact to traffic and general transportation infrastructure, there would need to be a huge amount of money spend and expropriation of property to support that infrastructure. Given the duration required to complete a project like this, and the cost, the likelihood of this happening when we elect short term governments looking for short term results is very unlikely. Even if one government got started, the amount of money they would be spending in a short period of time would probably bomb their chances of getting reelected, and the next government would campaign on not continuing the project, or at least changing the scope to the point of making it unrecognizable, cancelling contracts and wasting a ton of money in the meantime. Massive expansion of rail, both for transportation and shipping would be needed, at a minimum. Changing municipal rules to stop the NIMBY folks from stopping highrise buildings from being built near existing GO Train stations would be required as well.
Anyways, regarding HOV lane use, I'd like to see bikes be able to ride in the space between the HOV lane and the standard lane (the /// area) as they do in California. You essentially get your own lane, and it's quite effective. Given that people SHOULDN'T be crossing this area, it should be very safe for bikes to use (I understand the reality is different, but that's an enforcement issue, because cops would rather hand out speeding tickets).