I once had a 55 min connection time in BRU arriving from YUL onward into Schengen area. Flight took forever to taxi at YUL due to never-ending rain in late winter/early spring... pilot was not able to make up the time by flying alternate coordinates so by the time I landed, airline crew and the pilots had communicated so well I was handed a new boarding pass while exiting the plane in the gate tunnel. Customs line was non existent in the connections area and I was through within a minute... just a few questions, a stamp, and off I went.

Sucks for me as the next flight was 7 hours later but if they had just held the other flight just 5 mins I could've cleared customs and made the gate before the plane had to back out of the gate.

Weather is everything. 40 mins is tight when arriving on a Schengen flight (60 mins is much better), but BRU is small so one can navigate quickly!