The travel agent issued AC ticket looks like this:

YOW-IAD - Y (C fare basis) AC flight/metal (aircraft is RJ, so no bus class)
IAD-BRU - C (C fare basis) UA flight/metal
BRU-LHR - Y (C fare basis) AC flight, BD metal
LHR-YUL - M (M2CA fare) AC flight/metal
YUL-YOW - M (M2CA fare) AC flight/metal