
I'd imagine it would be rather unlikely with a breed as rarely seen as the Glen of Imal. :) More likely to be a cross of more common breeds.
Sometimes you just can't tell. I had an accidental litter between a Golden Retriever and a Malinois. 5 of the pups were black and looks like Labradors, and in fact several of the owners get into heated discussions when people tell them they "must have been had" as their dog "clearly is a labrador cross". The other pups were brindle and people usually tell me they must be Greyhound crosses. :) Nobody has ever guessed right.