Just an update on my experience interlining bags from YYJ - YVR- LHR - SNN. Everything worked well, AC in YYJ were able to check bags all the way through. Still had to run in YVR to make my connection but didn't have to re-check the bags and was able to stay air-side. Just a note even though AC were able to check the bags through they were not able to give me boarding passes for the YVR - LHR - SNN legs with BA but i was able to get these at the gate from BA in YVR.