If a county is not served by a community mental health center having the capacity to perform the required preliminary diagnostic evaluations, the regional administrator for the county shall arrange for the evaluations to be performed by an alternative diagnostic facility for the period until the county is served by a community mental health center with the capacity to provide that service. An alternative diagnostic facility may be the outpatient service of a state mental health institute or any other mental health facility or service able to furnish the requisite professional skills to properly perform a preliminary diagnostic evaluation of a person whose admission to a state mental health institute is being sought or considered on either a voluntary or an involuntary basis.