California Joint Custody: What happens if 50/50 parent moves?

If two parents have joint custody and one parent moves an hours drive away. Whose responsibility is it to transport the child to the other parent during the schedule switch? My husband moved within 3 miles of the mother of his daughter, to be closer to his daughter and her schools. Within a year, the mother moved to a town an hour away and now is insisting that we are responsible for driving at least halfway, to her, to pick up their daughter on his days. He has never agreed to such a thing and before she moved away she verbally said she would take all responsibilities for transporting their daughter. We share 1 car between the 2 of us and their exchange time is noon. He works from 9 - 5 every day and having to take out 2 hours to pick her up in the middle of his workday puts his job in jeopardy. When he can't get to her to pick her up her mother just keeps her for that day until he can pick her up and refuses to drive her to us.