On any of the EOS xx(x)D model that has the live view function, can the camera make focus using the AF collimators (instead of using contrast detection), as it's possible on the old Nikon D300 ? If yes, can you tell me wich models make this possible ? I don't find the answer of this question on the net. Thank you.
Most Canon DSLRs can do it. On the EOS 60D this is called Quick Mode, despite it not being quick at all. You just have to select the option in the Camera menu. The other option is Live Mode which uses contrast-detection.
It is called the same on the 7D and I believe very similarly on the T?i models as well but I don't have them here to check at this time.
In Live View, the mirror is up and the AF collimators do not have view of the scene and can't do any focusing. The EOS Quick Mode flips the mirror down, exposing the scene to the collimators and then flips the mirror back up. There isn't a way for a traditional mirror-equipped DSLR to show live view WHILE using the collimators to focus.
The Sony Alpha DSLRs DO do this, because they don't use a traditional mirror - they use a semi-transparent mirror. This splits incoming light to the collimators and the sensor simultaneously. This is why the newer Sony Alphas can shoot a high FPS while continuously auto-focusing, and why they use an Electronic View Finder. The EVF is used because the light entering an Optical View Finder would ruin the exposure/metering of the scene with the semi-transparent mirror setup and always (except when the shutters are active during exposure) exposed sensor.