I ask the question for the security lanes - whether for domestic, transborder, or international flights.
Of course, one can use the GE kiosks at US preclearance sites at Canadian airports. However, the GE card would be useless for nexus lane entry (through Canadian customs and immigration) into Canada.
Related to this issue - on the AC thread - a TSE precheck type lane for transborder security at T1, YYZ.
link:
http://www.flyertalk.com/forum/air-c...sborder-2.html