My midwife only refers for ultrasounds if she feels they are warranted. I've only had them with two, both due to possible postdates with my pregnancies and needing to check their water levels/placentas.
With my first pregnancy we interviewed her around 8 weeks and then had our first prenatal about a month later I think. She usually has me do my first appointment around 12 weeks.
I just started read Your Best Birth by Ricki Lake and Abby Eipstein and it might be something you would be interested in. The sub-title is 'Know All Your Options, Discover the Natural Choices, and Take Back the Birth Experience'. (FYI - There is some
in the text so if you are really offended by that you might skip it.)
My midwife dates pregnancies based on LMP, but would refer for an ultrasound if your measurements (fundal height) seemed to be off for your dates, or like me, your baby doesn't seem to be ready for the party by 42 weeks.
Midwives will differ on all this depending on state laws, what type of midwife you are using, where you plan on birthing, etc... My midwife only does homebirths and does not work with doctors directly, but will turn over care to the provider of my choice if needed. I've birthed twice in the hospital with the doctor on call due to a non-emergency transport during labor and a transfer of care prior to onset of labor for an arom induction & NICU care for my baby. Both times my midwife remained with me to act as my doula, but was not allowed to "deliver" the baby because she can't practice in the hospital.
I've never seen an OB for prenatal care, so I really don't know how they work exactly but routine ultrasounds and ve's are not part of midwifery care ime.