If Canada law allows for a restricted license, would that be honored in the US?

I don't really know. I've had a few clients who have received DUI's in Canada and it never has shown up on their MI record. One client, in particular, will not travel to Canada any longer because if he does, he is afraid that it may trigger something and MI would know. (his was about 5 years ago) He needs a Canadian attorney. It also depends on whether he was in his commercial vehicle, if not, I do not know why he would be arrested, but then again, I am not familiar with Canada drunk driving laws, sorry. His cdl is fine until he hears something from the Michigan Secretary of State. Of course, some companies require their employees to report themselves and some lose their jobs, even if they keep their cdl, because a drunk driving conviction will make many employers have to release him due to their auto/truck insurance premiums going up.

Get a Canadian DUI Attorney on board right away. They will know how the Canadian Courts work. I'm almost sure the US will recognize the Canadian case and take action here, so getting the proper representation there is huge.

Good question but I would have to research the answer. If Michigan and Canada reciprocate the restriction should be valid on both sides of the border. The fact that it was an infraction in Canada but would not have been in the US is quite germane and a "conflict of law". If the drinking and driving is reciprocated there could well be an issue which his CDL.

Call a qualified DUI lawyer immediately. The answer is complex. More facts are needed. The stakes are high on this one.