1D and FP High-Speed Flash Sync

I recently purchased a 1D and the normal flash sync speed is 1/500th. However, the manual states that it can also sync at higher flash speeds (the 1D has an electronically controlled hybrid shutter).

In a number of threads it has been reported that reliable sync speeds of up to 1/2,500th second can be achieved with the 1D:

http://www.fredmiranda.com/forum/topic/682287
http://www.fredmiranda.com/forum/topic/682287/0#6110456
http://www.fredmiranda.com/forum/topic/662846/#5911138

A few questions:

1. How do you sync at speeds higher than 1/500th second on the 1D?
2. Does the exposure exif metadata indicate the actual sync speed?

3. If the exif metadata is not accurate is there a way to determine the actual sync speed?

Thanks!