This sounds like why Sound Transit exists in the Seattle-Tacoma metro area. It basically creates an adapter pattern-like third agency that manages the long distance routes between the major cities and counties.
And they opted out because they would have had to pay in fully with no service for years, followed by inferior service forever (they were to be cash cows).
I was going to comment the same; I lived in Tacoma and committed to Seattle for 4 years, and it was incredibly convenient, even with the traffic on I5. The seattle-tacoma route had more frequent intervals than the local Tacoma busses did and the transit was pretty nice. Usually full but never packed (except last bus of the evening)
