(a) Any existing participating regional or local health care program may withdraw from participation in the Healthy Texas Program at any time by written notice filed with the commissioner on a form and in the manner prescribed by the commissioner.(b) Any existing participating regional or local health care program also must provide enrollees under the program written notice of its intention to withdraw from participation in the Healthy Texas Program not later than the 90th day prior to the anniversary date on which the withdrawal is to become effective.