§ 105-a. Immunity from civil liability for employees of public transportation authorities who render assistance to victims of crime. Notwithstanding any provision of law to the contrary, any employee of a public transportation authority who renders assistance to a person who is a victim of a crime being committed on any facility of such authority shall have immunity from civil liability for damages for injuries or death arising out of such act of assistance, unless it is established that such injuries were or such death was caused by gross negligence on the part of such employee.