Other extensions:
LHR-DUS
FRA-SXF [not local traffic though as I recall]
also FRA-DEL for a few flights

Extensions are considered to costly now. The airline absorbs all the cost of the run for an incremental increase in passengers. By giving them to the partner airline, you save all the cost and keep most of the revenue.

Now I am surprised to hear about YOW-YUL-LHR. I thought we had proved this as nonsense a long time ago. Same as YEG-YYC-LHR. Dash-8's carry the traffic much cheaper.