I've just finished (I hope at least) going through the hassle of trying to find a VBAC provider in Western Washington, particularly within the constraints of DSHS, so let me tell you all that I found out in the hopes that it will make your own search shorter!
I live in Kitsap County and my only health plan options through DSHS were Community Health Plan of Washington and Group Health (these are the same options available in Thurston as far as I know). Of all the providers who contract with CHPW in Kitsap and Pierce Counties, I only found one who would do a VBAC, an OB, Phoebe Hoh in Tacoma. Like AllisonK said, DSHS won't cover a HBAC, so licensed midwives are out (unless you want to pay out of pocket).
Eventually, I settled on Group Health because they position themselves as VBAC friendly and both their midwifery and OB teams have been supportive of me so far. However, the problem is that they contract with St. Joe's in Tacoma, and St. Joe's doesn't allow VBACs. Instead, they'll send you to Tacoma General, but that's no good because Tacoma General, being the regional trauma hospital is VERY interventive and conservative. They require continuous monitoring, IV, etc. What the Group Health providers recommend instead, is that those seeking VBACs go to their birth center at their Seattle hospital. From what I've heard from other VBAC mamas, the Seattle birth center is very VBAC friendly and supportive. So that's what we're doing, even though it means at least an hour of driving, maybe more. Probably, we will find a hotel room in Seattle as soon as labor starts and just wait for a while before going in so that we don't get stuck in rush hour in labor!
I met with a couple licensed midwives as well, but paying out of pocket is sadly not an option for us. Pam Golliet (Federal Way) was particularly awesome and I highly recommend checking her out. If it wasn't for the fact that DSHS won't cover a homebirth, I would hire her in a second (I'd much prefer a homebirth anyway!)
Anyway, I'm new here, just joined today in response to reading your request for Oly VBAC providers. I just wanted to share what my research has revealed so that you hopefully don't have to look so long and hard!
Good good luck!!!