I'm being pedantic, but it's not actually Canada's pipeline, it's a Canadian company's pipeline. We're not so far gone as to have the government take over the mean so oil production!
I suspect the bigger problem is that, rather that building pipelines that are very safe, Enbridge builds pipelines that are as inexpensive as possible. The company has a long history of spills and doesn't seem to be very interested in learning from experience.
Correct.
The other issue is that states do not have the power to tax the oil that moves through the pipeline.
That creates a situation where they have moderate incentives to allow new construction (some construction jobs and sales taxes), but little or no incentive to continue permitting legacy infrastructure.
The older the infrastructure, the more risk there is for states in the form of pollution, and it looks like all risk for little or no reward. Meanwhile, the oil companies have exactly the opposite incentive to maximize the return on their sunk costs.
So, here we are: Michigan gets nothing for allowing 1950s infrastructure to continue but the ROI to Enbridge is likely pretty high.
If states were able to tax oil passing through the pipeline directly, I suspect we'd have a whole lot more pipelines.