the laws change all the time, but one call to one licensed lay midwife should answer whether they are legal to attend for twins--last time I was pregnant they were, but the first time they weren't ... the lobbying in Salem is a heavy job, with the OMA better funded and established.
So, if they still are, you can choose a licensed midwife based on whether they are themselves comfortable taking on a twins birth and whether they have a working healthy relationship with a perinatologist.
If it's not currently legal for licensed--and this is going to sound SO weird but hear me out--it is legal for unlicensed, in Oregon. (We have a funky set of laws that way.) So, midwives who wanted to be free to attend twin births all the years that it was not licensable, and midwives who want to attend breach births (I think still unlicensable), would choose not to license--meaning they don't have the 'legitimacy' of the license (and therefore have a harder time gaining a client base), but they probably have more experience with the tricky births. Of course, the chances they are going to have a healthy relationship with a Doctor when they have rejected the licensing standards enforced by the OMA, seems unlikely. Licensed midwives can probably point you to unlicensed ones--I nearly had to call on one with my last birth because the baby waited until the last legal day to start labor (21 days late) ... my midwife gave me two numbers, since I was determined to stay out of the hospital unless I felt like something was going wrong.
My first birth I accidentally discovered an OBgyn that was herself a homebirth mom. Last time I saw her she was practicing at ... SW Women's Health Associates maybe? ... it was a building just south of Hwy 217 on Hwy 99, I think at Greenburg Rd, and there were two OBgyns and three nurse midwives on staff. Unfortunately her hospital was StV's ... at least at the time. I left her practice because the hospital contracts she had to sign to maintain her right to practice there required induction if the pregnancy went more then 2 weeks over (I knew mine would--intuition and all that) and C-section if the labor went more than 24 hours (mine did) ... plus by that point I was already not a big fan of hospitals anyhow because of the research I had done.
Hospitals are pretty good with C sections nowadays. The decision I reached (after leaving that OBgyn practice) was that I would labor very close to a hospital, and deal with the emergency transport if it needed to happen. I didn't want to be bothered with the rest of the hospital routine (especially the ultrasound monitoring) ... so I picked a birth clinic two minutes from its hospital, and if the attending surgeon thought I was a crackpot evil mother for my birth choices, I just wasn't gonna care.
I hope you can find a medical specialist and midwife partnership that really works. More and more the two 'sides' are talking together, and hopefully by this time they have started working together as well.
Good luck, God bless, I hope you have a WONDERFUL birth :).