With my birth 10 years ago, I asked my homebirth midwives if they knew an OB I could go to as back up, and they did!
He was way, way supportive of women wanting to birth at home (still is!) and had a team of midwives on his staff. I went to see them 3 times during my pregnancy just to 'check in' so to speak. Since they knew I was planning a HB, there was no pressure to do any testing.
So, when I needed to transport into the hospital with my midwife, I was met by the OB's midwife also, and the 2 of them were there for the birth. The OB's midwife was covered by my insurance, and we paid the HB midwife out of pocket.
If you can't find a supportive OB, and I know they are hard to come by...at least find out what hospitals and what OB/MW are covered on your plan. Have that list ready, and if you do go to the hospital give the list to then and they will see if any of them are there or on call. But usually, if you transport, and the hospital is on your plan, they will use one of the staff OBs/MWs, so you should be covered.