I noticed this sign up on Harumi Dori that says the bicycles are NOT allowed on the sidewalks on Ginza Dori. Keep in mind that though bikes are not prohibited on sidewalks in many areas of Japan, there are designated locations where they are specifically prohibited.
Also remember that though bikes on sidewalks are allowed when necessary, they basically belong on the roadway.
I wouldn't feel like riding on the sidewalks of central Ginza densely populated with pedestrians anyway.