Lawyers for HCA Inc. and a partnership of Vanderbilt University Medical Center and Maury Regional Hospital are set to square off before a state agency over rival proposals to offer radiation therapy services in Spring Hill, TN. Each applicant opposes the other's $7 million-plus project. The Vanderbilt-Maury partnership doesn't believe there's room for both, while HCA believes both should be approved but doesn't want the rival proposal alone to be approved by Tennessee's Health Services and Development Agency.