I need to export packages deployed in SSISDB by any means to make it automated; so a command line, C# or T-SQL would be fine. I don\'t want the manual way used by Visual Studio.
I finally got it. Use stored procedure in SSISDB "atalog.get_project" which will return project_stream. Save it to a file with ".zip" extension and extract the packages from it.
This is because as per Microsoft documentation (http://download.microsoft.com/download/1/7/5/175A7833-6F75-418D-8800-86D44D1D712D/[MS-ISPAC].pdf) the ISPAC file is based on OPC standard which is genuinely was invented by Microsoft and used for pptx, docx ... etc.
IsDeploymentWizard is a good option. You can see parameter usage by typing
IsDeploymentWizard -h
on the command line.