Yes they will when the tech is spread to them normally over time. It will spread to any county the capital has connections to so even if its not part of your duchy or hold by one of your count vassals it will spread there when time goes by and from those counties it will pass on others again when time goes by.
Note that placing a spymaster on the study technology mission in a county makes that county count as being adjacent to your capital for tech spreading purposes so your tech can spread even to backwater areas if they choose to spy on your county.