Except as provided in subsection (b) of this section, application for involuntary admission of an individual to a facility or Veterans’ Administration hospital may be made under this part by any person who has a legitimate interest in the welfare of the individual. If the Administration agrees to pay the appropriate expenses, application for involuntary admission to a facility of an incarcerated individual in an institution under the Division of Correction or the Patuxent Institution may be made under this part by the Division or the Patuxent Institution.