This is called "Shelter Allowance Program" by Revenu Quebec, to subsidize rental or home $ (yes, for low-income home-owners also). To help LOW INCOME (a) individuals 50 or over, or (b) families with kid(s), who has (1) filed income tax and (2) lived in Quebec for over 1 year. I cannot recall if the program requires/specifies immigrant/citizen, hope 楼主 will answer/correct me.
This program does not back-pay, only starts paying the same month u submit/they receive application FORM. U can only get the form by calling Revenu Quebec YOURSELF, then RQ mail u form. Hence, those who qualify should act ASAP. (I do not have their direct phone# with me. )
Any further question, (1) google for web info on the program, or (2) visit the centre on 1029 Clark, or (3) ask whatever social agency near you, IF THEY KNOW.