The 'provider' will tunnel everything coming from the client (which is you) that is directly connected to its physical interface.
The 'provider' won't differenciate its neighbor (which is you) has configured subinterfaces.
In addition, for subinterface support on a 6500 - you need a WAN module. You can't do it with regular line cards.
Regards,
Edison
Edit: With the 7600 platform, the 'provider' can do selective Q-in-Q. Not sure if your intended platform can do that.
But you may get away with subinterfaces on this case since each subinterface will map to a different encapsulated .1Q
http://www.cisco.com/en/US/docs/routers/7600/install_config/ES40_config_guide/es40_chap4.html#wp1644678