N.Y. Comp. Codes R. & Regs. tit. 4, § 4.11 – Contingent permanent appointments to encumbered positions.

(a) A position in the competitive, non-competitive or labor class which is temporarily vacant by reason of the leave of absence of the permanent incumbent, may be filled on a contingent permanent basis through transfer, reinstatement, reassignment or appointment from an appropriate eligible or reemployment list.
(b) An employee appointed on a contingent permanent basis shall have all the rights and benefits of a permanent appointment; provided, however, that, in the event of the return from leave of absence of the permanent incumbent, such contingent permanent employee shall displace; first, any temporary or provisional employee serving in the same title and work location under the jurisdiction of the same appointing authority; and second, the contingent permanent employee with the most recent contingent permanent appointment date serving in the same title and work location under the jurisdiction of the same appointing authority. Where there are no opportunities for displacement as provided herein, such contingent permanent employee may return to the position from which he or she is on leave, if any, and shall have his or her name entered on the appropriate reemployment lists for the title held on a contingent permanent basis. Additionally, such employee may request to have his or her name restored to the eligible list or reemployment list, if any, from which the contingent permanent appointment was made, if such list is still in existence.
(c) Upon a vacancy in an unencumbered position, which is in the same title and work location and under the jurisdiction of the same appointing authority, the contingent permanent employee with the earliest date of contingent permanent appointment shall be permanently appointed to such position.
(d) The appointing authority shall, at the time of appointment, advise an employee appointed to a position on a contingent permanent basis, in writing, that their continuous service in such position is contingent upon the continuing leave of absence of the prior permanent incumbent. Further, permanent contingent appointees must be advised of their right to a leave of absence, if any, and to permanent appointment, as provided in subdivision (c) of this section.
1. (1) A permanent employee who receives a contingent permanent appointment to a position under the jurisdiction of the same appointing authority shall be entitled to a leave of absence from his or her permanent position for the duration of such contingent permanent appointment; provided, however, that upon successful completion of the probationary period in the contingent permanent position, he or she may return to such permanent position only upon the return of the permanent incumbent, and there are no displacement opportunities as provided for in subdivision (b) of this section.
2. (2) A permanent employee who receives a contingent permanent appointment to a position under the jurisdiction of a different appointing authority shall be entitled to a permanent appointment to a position in his or her former title under the jurisdiction of such appointing authority, upon successful completion of the probationary period, if available at that time or at any time during the contingent appointment, from which he or she shall be provided with a leave of absence for the duration of their contingent permanent appointment; provided, however, he or she may return to such permanent position only upon the return of the permanent incumbent, and there are no displacement opportunities as provided for in subdivision (b) of this section.
3. (3) A contingent permanent employee may be given a leave of absence from his or her position. If the permanent incumbent returns to the position during the leave of absence of the contingent permanent employee, the right of the contingent permanent employee to return to such position is extinguished and such employee shall have the displacement and reemployment rights provided for in subdivision (b) of this section.
(e) Leaves of absence.
(f) A permanent employee may not be reassigned to an encumbered position unless the employee agrees, in writing, to accept a contingent permanent appointment to such position.
(g) This rule shall not apply to reassignments made pursuant to a reassignment list program approved by the Department of Civil Service.