https://en.wikipedia.org/wiki/Downtown_Seattle_Transit_Tunnel
Unlike in backwards Vancouver, a bus tunnel, a bus bridge, or a HOV crossing that is designed to eventually become part of a LRT conduit, makes sense.
https://en.wikipedia.org/wiki/Downtown_Seattle_Transit_Tunnel#Bus_tunnel
https://en.wikipedia.org/wiki/Downtown_Seattle_Transit_Tunnel#Opening_and_bus-only_operation
An express bus tunnel from downtown Vancouver to W. Vancouver & H. Bay would make sense. Especially, if it was designed to eventually be for a LRT crossing. Unfortunatly, backwards Vancouver & BC usually opt for the congestive planning choice.
