They are known in Africa to be asymptomatic carriers of the virus. ... and they're not known for what?
Infecting people with Ebola, that's what.
There isn't any difference between Ebola carried by a dog and Ebola carried by a human, so there isn't any reason a dog can't transmit the disease to a human being.
Dogs (like the other mammals that are the source of outbreaks) can carry the disease and be infectious for a time without showing symptoms.