Is the back Chassis for the Canadian Rogers I747M the same as I747 T999?
There's no such thing as an "i747 T999".  

The I747 is the model used by AT&amp;T.  There is no relevant difference between the i747 and the i747m used by Bell and Telus, or the i747R used by Rogers.  They're identical as far as software or repairs are concerned.

The T999 is a different model used by T-mobile, Wind Mobile, and possibly others.  The only real difference is the supported frequency bands, though this means they're not intercompatible for ROMs.  Casings are identical, as are common parts like the camera or screen.

I would presume that by "I747 T999", they mean the part is compatible with both the i747 model and the T999 model, which it should be, as the physical form of them is identical.