§ 156. Liability for a Prisoner on Work Release. No prisoner participating in a work release program or whose place of confinement is extended pursuant to this article shall be deemed an agent, employee or involuntary servant of the department or the city while employed or going to and from such employment or released from confinement pursuant to this article; provided, however, that where a prisoner is employed and paid by the city, his relationship to the city arising out of such employment shall be determined in the same manner as if he were a free person so employed.