The Canadian investment isn't altogether altruistic- the funds come with the promise that Canada will get paid back out of bridge tolls.
But opponents of the project say there isn't enough traffic to warrant the new bridge and that the projected revenue is optimistic. Peter Samuel of TollRoadsNews looked at the construction company bids on the project:
"The respondents strongly favor an availability payments model, whereby they get paid for providing the bridge and operating it, regardless of toll revenues. This means the major business risk is carried by the governments, not the investors.
The unwillingness of responders to take any risk on toll revenues suggests they are highly skeptical about it as a self-financing project."