as rika said :
why don't you create overlay that will open on epg on "enter" and will have whatever events you'll need like "close overlay and exit epg screen" or "close overlay and select whatever button outside of epg area" etc.
in the event to close this overlay, you can add a command "xlobby:button select" so when you will close this overlay, you will go back to the epg screen and the button that you want will be selected....
but me too I use also nav buttons for epg, just to be able to navigate in the epg using touchscreen ...
look at this screenshot:
what I did is: give an ID to the epg zone, then create an event for every nav buttons with the commands:
"xlobby:button select" (in the aim of select the epg zone)
+ a command "navigation:up" or "down" etc...
but this will not working with a remote... but maybe you can add another command in these events to select back your nav buttons...