The Holland Tunnel doesn't have marked edge lines, but the full barrier line in the center takes up 18" of width. Someone else would have to confirm the actual roadway width.
8'–10' lane widths definitely aren't unheard of in the NY metro area. Some sections of the Jackie Robinson Pkwy, Bronx River Pkwy, and Queensboro Bridge have lane widths in the 8'–9' range.
The lanes on the GWB feel wider because cars in lane 2 (and lane 3 on the upper level) can move to the extreme edge of their lane when passing vehicles in the driving lane and the passing lane, since there's no curb or barrier on either side of their lane.