Bone marrow transplants are usually performed in the pelvic bone or the sternum, so this procedure would not make the hip weaker or slower in healing from surgery. The issue
here would be related more to your father's health in general. I will assume your father had a bone marrow transplant for some type of cancer, but you did not mention in your question how long ago the transplant took place. Therefore, I will try to address new and old transplants and how they would hinder his recovery from surgery.
If the transplant is recent, and the cancer is still actively being treated, then there may be issues with slower healing. This would be related more to the cancer than the bone marrow transplant itself. Your father's oncologist could help address your concerns and help monitor your father while he is healing. You could contact them if they are not already involved.
If the bone marrow transplant was years ago, and the cancer is in remission, the recovery process for a broken hip should be pretty much the same for your father as everyone else, as long as he is relatively healthy.