My grandparents names were also John and Julia. However, they had several children, John, Peter, Mary and Genevieve Anne, who was my mother. It was difficult finding anything on them as Boyuk or Bojuk are very common names.
Have you checked the Canadian Census and Ship Manifests? Was your grandfather born in Sudbury or did he come over from another country? My grandfather was Ukranian.
And, I never found out my great grandparents names. I am sorry. I know how difficult it is. My mother immigrated to the US and I had my mother's social security and green card. I ended up going to the US State Department, Freedom of Information Act.
I don't know if this helps. Good luck with your search.
D. Colgan