Any error messages?

edit: when I look for examples of SSIS packages being executed by xp_cmdshell, I see that they are escaping the " in their code. Maybe you need to add that as well.

Example: http://geekswithblogs.net/stun/archive/2010/02/24/execute-ssis-package-from-stored-procedure-with-parameters-using-dtexec-utility.aspx