I'm not that familiar with Burnaby Mtn, but what are the leashing rules like? Even though I like dogs, I do not like them on mtn bike trails (especially when they're unleashed), let alone owners who will blame others for their dogs safety. The few times I've almost hit a dog, the owner was smart enough to put a bell on the collar and they were actually pretty understanding about the whole issue. It's even better when the owner see's a bike on the trail and a rider fighting his way out of the bushes.
If you know there's a junction, control your dog and save us all this bs. After all if you're dog gets hurt, you really have no one else to blame but yourself. You took up him/her up there, and let him roam around hoping everyone else has that mythical thing called common sense.
Here's the flip side to the OP - you said the rider could've killed your dog. What if you're dog caused the rider to eject, bail, and severely injured themself?
Flame on.
protect tom mcdonald at all costs