Ummm, I am fairly sure that they wont have OB's at the birth centre? As the whole point is that it is midwife-patient centered care.
You have to put your name in a ballot by your 12th week of pregnancy I believe. I think about 400-500 people apply every month, and only 40 are given a place.

I must say that the care there is fantastic...... it certainly doesn't 'feel' like a public service iykwim? I feel as if I am getting the absolutely best care, attention, support, and nurturing from my two midwifes. I can't recommend it enough, and really feel that all women should have the option of having this type of pregnancy care!