did some tests, not sure if you will not like what I have found.
7d with latest firmware 2.0.0.
ST-E3-RT in hot shoe, is recognised by the 7D as a "dum" device. It will trigger, but you can not get enable wireless.
EX 600 in hot shoe of the camera. Manually set the ex600 to radio control. Switch both 7D and Ex600 on.
Go to "external flash setting", enable wireless and the ex600 will switch automatically to optical.
After that I set ex600 manual again to radio control and it will trigger via radio the slave.
Switch the lot off and you will have to go through the sequence again.
Next issue: normal sync speed is 1/250 optical, but 1/125 radio controlled (says so in the manual!)
Next experiment, I have the wireless enabled on the 7d, manually set both ex600 to radio and HSS.
I am able to set shutter speeds to 1/8000 and I get proper exposure. I tried same shots with optical and exposure is the same.
For me, the biggest draw back is that all the functions that you have when using the ex600 in optical, so define ratio etc with the 7D menus, is not working in radio mode. You can fool the system by steps outlined above.
So, back to you original question, from my test it appears that you can do radio controlled HSS with the ex600 but you have to set it on the EX600.
Hope this helps
If you want more detail, just send me an e-mail