Salam,
I haven't heard about a case in which the visa office was Islamabad and then it got transferred to INDIA office, your husband needs to have one year Indian Visa Stamp on his passport before the MISSISSAUGA office is convinced that you husband's case can be sent to New Delhi office, When my wife applied for me this was the exact dilemma we were facing and because we took plenty of time planning our application and taking PRE and POST wedding photos, Skype Pictures before our wedding and after our wedding, pre wedding emails and post wedding emails and other stuff, we got Re-medical and Passport request from Islamabad office within a year, so do your homework and try to collect as much proof as you can before applying, Good Luck!