I believe Metro is only "outside" service in this market. I lost track of who owns what ... I believe CBS has one and Clear Channel has one ... and I'm thinking Metro is owned by Clear Channel now?
I think all stations that do traffic use Metro at least in the off-hours should they do traffic coverage at all in the off hours (KOMO, KIRO for example...where the music stations tend not to do traffic on weekends). Otherwise, KOMO and KIRO each have airborne person or person(s) during drive times...KING-TV also does their own airborne. Beyond that, all TV news and all morning drive tend to have a "team" person who presents the traffic during those morning shows...and in most cases those reports are derived from the state traffic flow maps, cameras, and audience phone-in tips.