It was announced on September 25, 2010 in New Delhi that Canada and India have completed negotiations for the signing of a Social Security Agreement between the two countries. After the agreement is signed, it must be ratified by the governments of both countries. That may be as early as 2011.
As was stated in a previous post by DanielBl, to qualify for the Old Age Pension in Canada, you must be a resident in Canada for at least 10 years. One of the purposes of an International Social Security Agreement is to provide credit for the years that an immigrant has lived or worked in his previous country of residence. Canada has signed almost 50 such agreements with countries around the world. When this agreement is ratified, your father may qualify for a partial Old Age Pension, ( formally referred to as Old Age Security ) and may qualify for the Guaranteed Income Supplement. To qualify for the GIS, the resident must also be in receipt of the OAS. The purpose of the GIS is to supplement the income of the OAS when the recipient has little or no income from other sources. Currently, if a resident has income less than $13,200 from other sources such as CPP (Canada Pension Plan ), employment income, private pension income including income from an RRSP, investment income, etc.and is in receipt of OAS, they will qualify for the GIS. It works on a sliding scale. Therefore, the more income from other sources, the less you qualify for GIS. In order to qualify for a full OAS, you must have lived in Canada after age 18 for 40 years.
Because the Canada -- India Social Security Agreement has not passed, I am unable to comment on it. However, I suggest that you contact Service Canada and speak to a representative in person. They probably cannot provide you with much information but maintain this contact and continue to follow the development of this agreement. Once this agreement has been passed and ratified by both governments, then begin immediately to pursue your father's application for OAS.
Good Luck and have a GREAT DAY