If I understand you correctly, you're using the EyeTV Remote "as-is" (without Remote Buddy) with EyeTV. In this case, if you press the "Live" button, the action triggered by it is controlled by EyeTV.

Opposed to this, the "Live" action in Remote Buddy has no link to the "Live" button on your EyeTV Remote. The "Live" action really only does what's written on its tin: jump to the live signal (just like as if you select "Live" from the EyeTV's pull-down menu).

I don't know what EyeTV is executing when you press the "Live" button on your EyeTV remote. But if its an AppleScript or application that's being executed in reaction to this, you should be able to create a custom action in Remote Buddy that executes the same AppleScript (or runs the application via AppleScript) and subsequently map that action to a button of your choice.

Best regards, 
Felix Schwarz