31. For the purposes of application of section 115.1 of the Act respecting the Government and Public Employees Retirement Plan (chapter R-10), an employee is deemed to be casual if he has been hired:(1) to hold a position which normally exists owing to a shortage or temporary absence of staff or an excess of work and which is remunerated in an essentially temporary manner;
(2) to hold a position for the purpose of carrying out a specific task of a fixed duration, except where the employment or the position is of a recurring and seasonal nature; and
(3) to fill a vacant position temporarily in the absence of eligible candidates.