Inuit will tie a sled dog bitch in heat so a wolf will mate with her. Genetic crossovers still happen.
I nu it!
I've personally looked into this and natural crossbreeding with modern wolves is very rare (isn't seen in genetic samples). This is probably due to the innate propensity of wolves to kill any non-pack member. Dogs tied out where they can attract wild animals are probably being used as bait. That's what I saw in that famous photo of the polar bear playing with the dog. Who knows how many dogs were eaten before they got that photo.