While implementing Sixth pay commission report, Finance Ministry vide its O.M No: 2(13)/2008-E.II (B) dated 04.03.2011 dated 29.08.2008 decided that special dispensation of grant of HRA has been allowed to continue to (i) Faridabad, Ghaziabad, Noida and Gurgaoan at "X' class city rates and (ii) Jalandhar Cantt, Shillong, Goad and Port Blair at "Y" class city rates
Also, special dispensation allowed to Panchkula for grant of HRA at par with Chandigarh vide this Ministry O.M.No: 2(2)/2001-E.II (B) dated 16.06.2003 shall also continue.
It is also clarified that any other similar special dipensation allowed by Finance Ministry in the past in respect of other cities of for grant of HRA at higher rates and not specifically mentioned in this Ministry's O.M. of even number dated 29.08.2008, shall continue to apply, if the same has not been superceded/dispensed with or the existing classification of such city has not been revised to a higher classification with or the existing classification of such city has not been revised to a higher classification account of of the population criteria has not been revised to a higher classification on account of population criteria vide O.M dated 29.08.2011
For more details download this Office memorandum No: 2(13)/2008-E.II (B) dated 04.03.2011