If Subaru Canada wants to interact with people on car discussion forums, they could do best by joining the Subaru-specific sites and participating there. That would REALLY help their customers and attract new ones.
The same goes for the other car manufacturers. While there is occasional participation in specific-brand discussion sites by "lower" ranking people, such as a mechanic at a dealership, the supposedly Internet-smart manufacturers universally avoid direct participation in these sites. And these sites voluntarily support their brands and their customers. Odd, perhaps even dumb.