If you're still a PM, you should have SC access at DTW as a STE+ member regardless of your class of service as it is same day international. Even if Canada was considered domestic, that benefit does include same-day domestic flights that are connecting onward to international connections. Should work the same way on your return.

I believe you have to be in first or business on the international segment of the itinerary to receive SC access that way, but I have no idea how Premium Select fits in there.