Welcome. As a public transit user myself I have to be keenly aware of the issues involving carry on a bus. Under state law, you must have a Washington State CPL or a legally recognized permit under RCW 9.41.073 to be able to carry a loaded pistol in ANY vehicle, that includes public transit buses and light rail trains, and I presume the ferry boats too.
Though I have had contact with Pierce Transit, Everett Transit, Community Transit, and Sound Transit on the issue, I have not had contact with Kitsap Transit thus far on this issue. Nor have I had contact with the Bremerton and Kitsap authorities.
Kitsap Transit Code of Conduct
They follow state law. That does not mean neccesarily that a driver will not know these rules, or think that open carry is flat out illegal (I won't even get into the discussion over RCW 9.41.270 right now).